In the following questions, a sentence has been divided into four parts and marked a, b, c and d. One of these parts contains a mistake in grammar Idiom or syntax. Identify that part and mark it as the answer.

A. Though his choice was neither economics or politics

B. he had to study one of them,

C. because the science class had already been filled

D. and there was no other hope for him

Please do not use chat terms. Example: avoid using "grt" instead of "great".