1. There are large _____ (数量) of rain in the area of the country every summer.
2. Scientists have many theories about how the universe first came into _____ (存在)．
3. A rainbow is a natural _____ (现象) especially after a heavy rain.
4. Such a mistake would perhaps lead to disastrous _____ (结果).
5. The _____ (平均数)of 4, 5 and 9 is 6.
