This is a test of commonsense with single/multi-choices. Complete the next sentence:

A group of people are riding rafts through a cavernous river. They paddle as they glide past large cliffs. they

OPT: a). slowly float through a narrow canyon filled with rapids. b). go under an empty space in the rocks. c). ride through mountains on their boards. d). go up and down the steep river above.
The answer is:
b).