单项选择题
The local government tried its best to ensure each of its citizens a（）supply of food at regular intervals (时间间隔).
A.consistent B.continual C.continuous D.numerous
单项选择题 The United Nations Conference on Global Environment, which took place earlier this year in Vienna, was a very（） meeting.
单项选择题 We watched the plane（）behind the clouds.
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.
