Fill in the blank with the correctly spelt word. The phenomenon could be explained by ________ fluctuations.

Correct — D. Build the word from its two Greek parts: thermo- (heat) + dynamic (power, force).

Each part keeps its own spelling: o at the end of thermo, a y and one n in dyn, and the adjective ending -ic.

Thermodynamic gets all four right, and thermodynamic fluctuations, changes in heat and energy, can explain a phenomenon → option (d).

Why the others are wrong

• (a)
  thermodinamick — thermodinamick makes two errors: an i where dynamic has a y, and an -ick ending where the adjective suffix is -ic, as in dynamic and electric.
• (b)
  thermadynamic — thermadynamic changes the linking vowel. The heat prefix is thermo-, with an o, as in thermometer and thermostat.
• (c)
  thermodynnamic — thermodynnamic doubles the n. Dynamic has a single n, like dynamo and dynamite, which come from the same Greek root.

A spelling cloze gives a sentence and four near-identical forms of one word. The sentence only fixes the part of speech, an adjective before fluctuations, so meaning cannot choose; the letters must.

Long technical words are easiest to spell by their parts. Thermodynamic is thermo + dynamic, and you already spell each part in thermometer and dynamic.

Checked part by part, every wrong option shows its fault at once: a wrong linking vowel, an i for y, a doubled n, an -ick ending.

Key facts

• Thermodynamic = thermo- (Greek thermē, 'heat') + dynamic (Greek dunamis, 'power').
• The prefix thermo- keeps its o: thermometer, thermostat, thermodynamic.
• Dynamic has a y and a single n: dynamic, dynamo, dynamite.
• The adjective suffix is -ic: dynamic, electric, magnetic.

Common traps

• Spelling dynamic by sound: its first syllable sounds like 'die', which invites an i, but the Greek root gives y.
• Doubling the n in dynamic. It has one n, like dynamo.

No directly related past PYQ was found.