In the following questions, a few sentences are given. Identify the sentences that are grammatically and contextually correct.

(I) The children was playing in the garden while their parents watched.
(II) By the time we arrived, the concert had already started.
(III) Neither of the candidates were prepared for the final interview.

The correct option is Only (II).

Let us analyze each sentence individually to check for grammatical accuracy and contextual correctness:

Sentence (I): "The children was playing in the garden while their parents watched."
• Analysis: The subject of the clause is "The children", which is a plural noun. Therefore, it requires the plural auxiliary verb "were" instead of the singular "was".
• Correction: "The children were playing in the garden while their parents watched."
• Status: Incorrect.

Sentence (II): "By the time we arrived, the concert had already started."
• Analysis: This sentence uses the past perfect tense ("had already started") to describe an action that was completed before another past action ("we arrived"). This usage of tenses is grammatically correct and makes complete sense contextually.
• Status: Correct.

Sentence (III): "Neither of the candidates were prepared for the final interview."
• Analysis: The pronoun "Neither" functions as a singular subject when followed by "of the [plural noun]". Thus, it requires a singular verb ("was") rather than a plural verb ("were").
• Correction: "Neither of the candidates was prepared for the final interview."
• Status: Incorrect.

Therefore, only sentence (II) is grammatically and contextually correct.