The correct option is B high
Adverbs modify verbs, adjectives and sometimes other adverbs in a sentence.
In this sentence, the adverb 'high' is being modified by the adverb 'enough'. It states the extent to which the person is jumping high. So, option D is correct.
Option A is incorrect as the verb 'are jumping' is not being modified by the adverb.
Option B is incorrect as 'enough' is the modifying adverb in this sentence.
Option C is incorrect as adverbs don't modify pronouns.