The sentence written in active voice is:
"Harvey waved from the parade float at all the cheering spectators."
Explanation:
1. In active voice, the subject of the sentence performs the action. In this case, "Harvey" is the subject who is performing the action of "waved."
2. The sentence is structured in a way that clearly shows Harvey as the one waving from the parade float.
This sentence is in active voice because it clearly states who is performing the action, which is Harvey waving from the parade float.