I am pretty sure that the sentence which corrects this statement for active voice and maintains the same idea is the sentence from the last option represented above : He gave several reasons to support his viewpoint. I consider this one as a correct because active voice is when the verb of the sentence performs the action, in this case the verb is 'gave'. Hope it's clear!
Answer: D, He gave several reasons to support his view point
Explanation: It uses an active voice while still keeping the same meaning or topic, it also still supports the sentence that tells you that his reasons help his viewpoint.
