Answer:
The correct answer is D. past perfect progressive.
Step-by-step explanation:
The verb tense used in this sentence is the past perfect progressive because it is possible to notice the following word order: subject + had been + progressive verb form + complement. "Miranda" is the main subject of the sentence, "had been" is the past perfect form, "mountain biking" is the action being done and in which the verb "biking" is in the progressive form, and the rest of the sentence is the complement made of other verb forms and phrases.