Amba and Uma . . . . . . . . sisters. A. are B. which C. had D. was

The other options are incorrect for the following reasons:

• Option B, “which,” is a relative pronoun. Relative pronouns are used to introduce a clause that provides additional information about a noun or pronoun that has already been mentioned. In this case, there is no noun or pronoun that “which” could refer to, so it is not the correct answer.
• Option C, “had,” is the past tense of the verb “to have.” The sentence is not about the past, so it is not the correct answer.
• Option D, “was,” is the past tense of the verb “to be.” The sentence is not about the past, so it is not the correct answer.