Each of the letters in the word LAPTOP is arranged in alphabetical order. How many letters are there in the English alphabetical series between the letter that is fourth from the left and the one that is first from the right in the new letter-cluster formed?

Correct — C.
Rule: sort the letters, pick the two positions, then count the letters strictly between them.

LAPTOP sorted: A L O P P T (both P's stay).
4th from the left: P (16).
1st from the right: T (20).
Between them: Q, R, S → 20 − 16 − 1 = 3 → option (c).

Why the others are wrong

• (a)
  Two — Two undercounts. P and T are four places apart, so Q, R and S all sit between them: three letters.
• (b)
  Four — Four is the gap T − P = 20 − 16, not the count between. Letters strictly between are the gap minus one: 3.
• (d)
  One — One letter lies between letters two apart, such as R and T. Here the pair is P and T, four apart, with Q, R and S between.

These items chain three small steps: rearrange the word alphabetically, locate two positions in the new cluster, then count alphabet letters between them.

The count between two letters is larger position − smaller position − 1, because neither end is included. Repeated letters stay in the sorted cluster: LAPTOP gives six letters, A L O P P T, not five.

Key facts

• LAPTOP in alphabetical order: A, L, O, P, P, T.
• P = 16 and T = 20 in the alphabet.
• Letters strictly between positions m and n (m < n): n − m − 1.

Common traps

• Answering with the difference 20 − 16 = 4 instead of the letters between, 3
• Reading the 4th letter from the right (O) instead of the left, which puts four letters between O and T

No directly related past PYQ was found.