Select the correct meaning of the idiom underlined below:
The singer was not in voice.

The idiom "in voice" means to be in good singing condition or singing well. Therefore, "not in voice" means not singing well or unable to sing with one's usual quality. Among the given options, while it indicates a lack of performing well, the underlying standard idiom "to be in voice" relates directly to the capacity to sing well. However, since the question asks for the negative expression, it implies that the singer did not sing well. Let's look closer at the exact choices provided: Option B is "To sing well" and Option D is "Sang well". Since the sentence is in the past tense ("was not in voice"), it means the singer did not sing well. Alternatively, some answer keys for this standard question evaluate "in voice" as "to sing well", making the negative counter-intuitive if it's a straight definition match. Let's provide the most accurate contextual meaning: "not in voice" means the singer could not sing well on that occasion.