Read the following paragraph and write TWO irrelevant sentences on the answer sheet. 　There are few places on Earth where people need not be concerned about flooding. Any place where rain falls is vulnerable. Drought can also cause great damage. A flood occurs when water overflows land that’s normally dry. This can happen in various ways. In most cases, floods occur when rivers or streams overflow their banks. Coastal flooding occurs when a large storm or tsunami (海啸）causes the sea to surge inland. Most floods take hours or even days to develop, giving residents ample time to prepare or evacuate. Others develop quickly and with little warning. Excessive rain or rapid ice melting in the mountains is also an ideal source for generating electricity. These flash floods can be extremely dangerous, instantly turning a murmuring brook into a thundering wall of water and sweeping everything in its path downstream.