Direction: In these questions, sentences are given with blanks to be filled in with an appropriate word(s). Four alternatives are suggested for each question. Choose the correct alternative out of the four alternatives.
His wife has a twin who resembles her so much that at first he had great trouble telling ________

Options

A. 1) one from the other
B. 2) one from another.
C. 3) each other.
D. 4) who is which.

Answer

D

Explanation

who is which is used for talking about distinguishing one person or thing from another.
Here, who is which is the right usage.