11.Nature has a perfect system for recycling(循环) water. Water is used again and again. It falls as rain. Then it goes one of the three places. It might seep slowly through the soil as it soaks through into the natural reservoirs underground. It might disappear into the air by evaporating（蒸发） quickly. It might run off into streams（溪） to rivers and to the oceans. 问题：Nature has （ ）
A. a balance system
B. a system of recycling water
C. a rule to follow
D. a fate for human
