单项选择题
Pipes made of plastic are now widely used in building as they are light and do not become （）in water.
A.ripe B.instant C.rotten D.mature
单项选择题 They were under the（）that the company was doing well, but in fact it was in serious trouble.
单项选择题 This lovely old town has a（）you couldn't find in a big city.
单项选择题 The starter (赛跑发令员) gave the（） for the race to begin.
