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. The creature on Mars, if any

B. are bound to be very different from us

C. not only in shape but also in size

D. because of different gravitational conditions

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