UPPSC 2025 Prelims GS Paper-I · Question 126 of 150

Correct — D, both (A) and (R) are true and (R) is the correct explanation of (A). Read that option text before you do anything else, because this booklet has swapped the code you have drilled: here (d) is the 'both true and R IS the explanation' slot and (a) is the 'both true but R does NOT explain A' slot — the exact reverse of the ordinary UPSC arrangement. Now the substance. The Assertion is true and needs no defence: adult male and adult female voices differ audibly, and the difference is measurable. The pitch we hear is the fundamental frequency at which the vocal folds open and close, and it averages roughly 125 hertz in an adult man against roughly 210 hertz in an adult woman, with children above 300 hertz. The Reason is true as well. The vocal folds of an adult male are about 1.75 to 2.5 centimetres long; those of an adult female about 1.25 to 1.75 centimetres. The male folds are also thicker and more massive. And the Reason does explain the Assertion, because the vocal folds obey the same law as any other vibrating body under tension — the frequency falls as the vibrating length increases and as the mass of the vibrating element increases, and rises as the tension increases. Longer and heavier folds therefore vibrate more slowly, and a slower vibration is a lower pitch. This is the same physics that makes the thick, long bass string of a sitar sound deeper than the thin, short treble string. The anatomical difference is not merely a fact standing beside the audible difference; it is the cause of it. Both statements are true and the Reason is the correct explanation of the Assertion — and on this paper that is option (d).

• (a)Both (A) and (R) are true, but (R) is not the correct explanation of (A) — This is the trap the booklet is built around, and it catches the candidate who reasons perfectly. Work the substance out correctly — both statements true, and the Reason is the cause of the Assertion — then reach for the position that verdict occupies on an ordinary UPSC paper, and you land here. On this booklet (a) carries the opposite meaning. On the merits it is wrong too: the Reason is not an unrelated true statement sitting beside the Assertion. Delete the difference in fold length and thickness and the difference in voice disappears with it, which is precisely what an explanation means.
• (b)(A) is true, but (R) is false — The Reason is not false. The dimensions are measured, not inferred: adult male vocal folds run about 1.75 to 2.5 centimetres and adult female folds about 1.25 to 1.75 centimetres, and the male folds are the thicker and more massive pair. The visible sign of the same growth is the laryngeal prominence, the Adam's apple, which appears when the larynx enlarges at puberty under the action of androgens.
• (c)(A) is false, but (R) is true — The Assertion is not false. Male and female voices differ in a way that can be put on an instrument: the average fundamental frequency is roughly 125 hertz for adult men and roughly 210 hertz for adult women, close to an octave apart. Ranges do overlap at the margins — some men speak high and some women low — but the question says the voices are different, not that every man is lower than every woman, and as a general statement it is plainly correct.

Speech begins in the larynx, the voice box seated at the top of the windpipe. Air driven up from the lungs forces the two vocal folds apart; their own elasticity and the drop in pressure between them snap them shut again, and this cycle repeats hundreds of times a second, chopping the airstream into a buzzing tone. The rate of that cycle is the fundamental frequency, and the ear reads it as pitch. What sets the rate is the same set of variables that governs any vibrating string: frequency falls as the vibrating length grows and as the mass of the vibrating element grows, and rises as tension grows. So longer, thicker, heavier folds give a deeper voice, and the throat and mouth above them then act as a resonating chamber that shapes the buzz into vowels and consonants.

Take the item in three steps. Is (A) true on its own? Yes — the difference is audible and measurable in hertz. Is (R) true on its own? Yes — the fold dimensions differ, and the numbers are textbook. Does (R) account for (A)? Apply the deletion test: if the fold lengths and thicknesses were identical, would the voices still differ in pitch? They would not. The Reason is not a companion fact, it is the mechanism. That gives 'both true and R explains A' — and only then do you look at the printed code, which on this paper puts that verdict at (d). One honest refinement worth carrying: fold size is not the only thing that differs. The whole vocal tract above the larynx is longer in men, which lowers the resonances and gives male and female voices a different quality as well as a different pitch. That does not weaken the Reason, because the question is about the difference in voice and the fold dimensions are the principal determinant of the pitch that makes the difference obvious.

• Adult male vocal folds are about 1.75 to 2.5 centimetres long; adult female vocal folds about 1.25 to 1.75 centimetres, and the male folds are also thicker and more massive
• Average fundamental frequency of the voice is about 125 hertz in an adult man, about 210 hertz in an adult woman and over 300 hertz in children
• The frequency of a vibrating fold, like that of a string, falls as its length and mass increase and rises as its tension increases — which is why longer, heavier folds give a deeper voice
• The change is driven at puberty by androgens, testosterone chief among them: the larynx enlarges, the thyroid prominence or Adam's apple appears, the folds lengthen and round out and the lamina propria beneath the epithelium differentiates into three distinct layers
• The pitch we hear is the frequency of vocal-fold vibration; the vowel and the timbre are added above by the resonating cavities of the throat, mouth and nose, which are also longer in men

• The inverted code in this booklet. Here (d) means 'both true and R IS the explanation' while (a) means 'both true but R does NOT explain A'. A candidate who reasons the substance out correctly and then applies the remembered UPSC layout marks (a) and loses the mark
• Attributing the deeper male voice to bigger lungs or a larger chest. Lung volume affects how long and how loud you can speak, not the pitch; pitch is set at the vocal folds
• Confusing pitch with loudness and quality. Pitch is frequency, loudness is amplitude, and quality or timbre comes from the pattern of overtones — three independent properties that examiners like to shuffle

UPPSC repeatedly builds assertion-reason pairs out of everyday body physics — a familiar observation paired with the textbook mechanism behind it — so the skill being tested is causal direction, not recall. UPSC prefers to ask the same physics without the body: the inverse relation between the length of a vibrating column and its frequency, or which property distinguishes two instruments playing the same note.

• practice — not a real PYQ

  The pitch of the human voice is determined chiefly by

  • (a)the volume of air held in the lungs
  • (b)the frequency of vibration of the vocal folds
  • (c)the loudness with which air is exhaled
  • (d)the length of the trachea

  Answer(b) the frequency of vibration of the vocal folds — pitch is frequency, and the folds set it; lung volume governs duration and loudness, not pitch.

• practice — not a real PYQ

  The deepening of a boy's voice at puberty is caused mainly by

  • (a)enlargement of the lungs and the chest cavity
  • (b)growth of the larynx, with lengthening and thickening of the vocal folds under androgens
  • (c)thickening of the tongue and the soft palate
  • (d)an increase in the size of the nasal cavity

  Answer(b) growth of the larynx, with lengthening and thickening of the vocal folds under androgens — the enlarged larynx also shows outwardly as the Adam's apple.