Answer:
Assuming this question refers to the first clause, "because she was being chased", the answer is Passive Voice.
Explanation:
In the passive voice, a sentence will focus not on who performed the action, but on who received it or suffered the consequences. We have a subject, the verb "to be" functioning as an auxiliary, and the main verb in the past participle form. That is precisely what we have in "because she was being chased". That same clause, in the active voice, would be "because someone was chasing her" or "because they were chasing her".
Note: the second clause of the sentence, "Mariah fell down," is in the active voice.
