The sentence that is in the active voice is the one that reads as follows: Hail pelted the roof.
Explanation:
In most English sentences with an action verb, the subject performs the action denoted by the verb ("Hail pelted the roof"). Because the subject does or acts upon the verb in such sentences, the sentences are said to be in the active voice. You can change the word order of the sentences so that the subject is no longer active but being acted upon by the verb or passive ("the roof was struck by hail", "the roof is being pelted by hail", and "the roof was pelted by hail"). The sentence above contains the doer of the action (Hail) and the object receiving the action (the roof). The subject is perfoming the action denoted by the verb. That is why the sentence is active.
