Question

select the part of the subject that agrees with the bold verb. whenever spongebob squarepantss track coach isnt looking, the runner with neon blue sneakers strikes a silly pose.

Explanation:

The verb "strikes" is singular, and the singular part of the subject is "the runner". The prepositional phrase "with neon blue sneakers" is just additional information about the runner and does not affect subject - verb agreement.

Answer:

the runner