单项选择题
A.is it B.isn't it C.is he D.isn't he
A.pilot B.speaker C.standby wheel D.automatic pilot
A.large cumulonimbus (thunderclouds) building up B.high cirrus clouds gradually changing to cirrostratus and then to altostratus C.fog caused by the warm air passing over the cooler water D.low dark clouds accompanied by intermittent rain