Which of the following sentences is written in active voice?
the bike sped down the road as the boy pedaled it quickly.
the empty street was full of boys racing their bikes down it.
we went bike racing after school was over.
trying to build up speed, the girl pedaled harder.
not c

Hm, are you sure you got the question right? Because all of the sentences are written in active voice! Active voice is essentially everything that is not in the passive voice, and I don't see any passive voice here.

Passive voice would be formed with subject+form of "to be" + past participle,

and we have no example of this. All of the sentences here are in active voice.

Rhyme and rhythm are the correct answers.