hELP WITH ENGLISH?

1) On the first day that we ventured into the wilderness, our native guides took us to a deep canyon surrounded by steep cliffs of coppery, red rock. (2) On horseback, we began a long and perilous trek down to the canyon's floor. (3) The narrow paths were hardly visible, and we were often frightened by the heights. (4) Surely each of us could have easily fallen to his death. (5) However, the strange and new plants and animals we encountered along the way were fascinating, particularly to Ramirez. (6) Often, he asked us to pause while he sketched a specimen or attempted to gain pertinent information from our guides.

Which word signals the fact that the author found the journey interesting as well as scary?

A. however
B. perilous
C. surely
D. heights