Read each sentence to find out whether there is any grammatical or idiomatic error in it. The error, if any, will be in one part of the sentence. The corresponding letter of that part is the answer. If the given sentence is grammatically and contextually correct, then choose “No error” as the correct answer. (Ignore errors of punctuation, if any.)

The committee has (A) / decided to postpone (B) / their meeting (C) / until the next week. (D)

Correct option is C

The sentence has a grammatical error in part (C).
In this sentence, "committee" is a collective noun, which refers to a group of people. Collective nouns can be singular or plural depending on whether the emphasis is on the group as a whole (singular) or on the individuals within the group (plural).
In this case, the emphasis is on the group as a whole, so the correct pronoun to use is "its" which is the possessive form of "it".
Therefore, the correct pronoun to use in part (C) is "its" instead of "their".
Hence, the correct sentence formed will be "The committee has decided to postpone its meeting until next week."