Which words make up the adverb phrase in this sentence?

We built a giant snowman in the backyard yesterday afternoon.

a. We built

b. a giant snowman

c. yesterday afternoon

d. in the backyard

Actually, i see two such phrases: c and d.

an adverb phrase describes, among others, how, when and where something is done: so c. describes the "when" and d. decribes the "where" - and both are adverb phrases.

If I had to choose, I would go for c. as it actually includes an adverb; yesterday