Answer:
The verb "became" is a linking verb.
Step-by-step explanation:
The bolded word in the sentence above is became;
Became, as used in the sentence acts as a linking verb.
A verb is said to be a linking verb if it describes the subject by connecting it to a predicate adjective or predicate noun.
Here, the verb "became" describes the crowd as being restless and it also linked their restlessness to their waiting for the commencement of a concert.
So, "became" as used in the above sentence and also going by the description above, the very is used as a linking verb.