Which words in the sentence make up the adverb phrase? Which words do the adverb phrase modify?

A herd of elephants can cover 50 miles a day during the summer.

A.

A herd of elephants; modifies can cover

B.

during the summer; modifies 50 miles a day

C.

during the summer; modifies can cover

D.

can cover; modifies A herd of elephants

The words in the sentence which make up the adverb phrase and the words it modifies are:

B. during the summer; modifies 50 miles a day

Adverbial phrase starts with an adverb; in this case, adverb "during" is used which tells when the action takes place. Like the function of adverbs, it modifies verbs, adverbs, and adjectives which in this sentence gives more details about the phrase "50 miles a day".