Question

Which words in the sentence make up the adjective phrase?

The Grand Canyon is a steep-sided canyon with a river.









A.
a river







B.
is a steep-sided canyon







C.
Grand Canyon







D.
with a river

Answer 1

I'd go with B.
The reason I would is because an adjective phrase describes the subject. This is the best way of describing the subject, The Grand Canyon.

Answer 2

Everything else is just what it is, not EXACTLY describing it.