Which choice contains the past tense form of the verb to experience that would correctly fill in the blank in the following sentence? I _____ a lot of great things on my trip abroad last summer.

The correct choice is the past tense form of the verb "to experience," which is "experienced." In the context of the sentence, using the past tense indicates that the action of experiencing great things occurred during the trip abroad that took place last summer. The sentence is referring to a completed experience rather than an ongoing action or a habitual action, which is why "experienced" is appropriate here.

Using "experiencing" would imply that the action is currently happening, whereas "experiences" is a present tense form that does not fit with the past context of the trip. "Experience," in its base form, would also be incorrect since the sentence requires a past action. Thus, "experienced" is the only option that correctly conveys what happened in the previous summer.