What word or phrase is modified by the prepositional phrase in the sentence below?

Deidre asked the workers why they were working so early in the morning.
A.
working
B.
early
C.
asked
D.
workers

The word modified by the prepositional phrase "in the morning" is "working". So, the correct answer is A. working.

The prepositional phrase in the sentence is "in the morning", and it modifies the adverb "early." So, the word or phrase modified by the prepositional phrase is B. "early."

A. working