Question

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

Explanation:

The verb "steam" is plural - form. The subject "the bowls of clam chowder" is plural, agreeing with the verb in number. "While Ned Flanders waits for them to cool" is a subordinate clause and not part of the subject - verb agreement focus here.

Answer:

the bowls of clam chowder