As night fell over the valley, a cold rain began, and the disheartened hikers complained bitterly about blisters, wet boots, and a lack of hot food.

Which word or words in the sentence help readers understand that disheartened means "discouraged" and "on the verge of giving up"? (3 points)

a
night fell

b
over the valley

c
complained bitterly

d
wet boots