根据课文原文，填入所缺内容。
★ It was not immediately obvious that water was 1 the development of life.
★ This produced ____2____, which made it possible for life to develop.
★ I earned my passage by working as an unpaid hand, which ____3_____.
★ When they crossed the Rocky mountain, they 4 some mountain goats and even a grizzly and an eagle.
★ Many of them _____5_____riding wild horses and can win thousands of dollars.