A:正反应吸热,L是气体
B:正反应吸热,L是固体
C:正反应放热,L是气体
D:正反应放热,L是固体或液体
—Hurry up. The bus is coming.
—Wait a minute. Don't cross the street _______ the traffic lights are green.
将一副直角三角尺如图放置,若∠AOD=20°,则∠BOC的大小为( )