Question

select the part of the subject that agrees with the bold verb. while margot robbie waits for them to cool, the bowls of clam chowder steam at the table.

Explanation:

In subject - verb agreement, the verb agrees with the main subject. Here, "the bowls" is the main subject of the clause with the verb "steam", and "of clam chowder" is a prepositional phrase modifying "bowls".

Answer:

the bowls