Directions: In the sentence below, identify the part containing a grammatical or idiomatic error, if any. Ignore punctuation errors.

Most volunteers was (A) / present at the community centre (B) / after the holiday break, and (C) / the evening classes resumed (D) / No error (E)

The correct option is A.

Step-by-Step Explanation:
1. Analyze Part (A): The phrase in part (A) is "Most volunteers was". Here, the head noun "volunteers" is a plural countable noun, making the complete subject "Most volunteers" plural.
2. Identify the Error: According to the rules of subject-verb agreement, a plural subject must agree with a plural verb. The past-tense verb "was" is singular, which conflicts with the plural subject "Most volunteers".
3. Correction: The singular verb "was" must be replaced with the plural verb "were". The grammatically correct sentence should read: "Most volunteers were present at the community centre after the holiday break, and the evening classes resumed."

Therefore, the grammatical error is contained in part (A).