Which principal part is this verb form?
jumped
a. past
b. past participle
c. present
d. present participle

The most probable answer and the most likely one that you'd get would be either A. past or B. past participle.

As to why, the word jumped is both correct as a past and past participle. Its present would be just jump or jumps, depending on the subject the moment that it is used. As a present participle, it should be on its -ing form which is jumping. Thus, when determining the correct answer for this, there might have been a given sentence as to how it was used or something else. Either way, jumped is both past and past participle.

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