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
单项选择题The starter (赛跑发令员) gave the() for the race to begin.
A.advice B.signal C.glow D.attention