The local government tried its best to ensure each of its citizens a（）supply of food at regular intervals (时间间隔).

单项选择题The United Nations Conference on Global Environment, which took place earlier this year in Vienna, was a very（） meeting.

A.productive
B.communicative
C.aggressive
D.protective

单项选择题We watched the plane（）behind the clouds.

A.disappearing
B.disappeared
C.diving
D.dived

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.

A.conclusion
B.expression
C.enjoyment
D.illusion

单项选择题This lovely old town has a（）you couldn't find in a big city.

A.condition
B.standard
C.situation
D.charm