When he arrived at the bus stop, the bus ________ for 10 minutes.
A:has left
B:had left
C:has been away
D:had been away
属于混合物的是____,属于单质的是____,属于化合物的是____,属于氧化物的是____。(请用序号填空)
如图,已知AB⊥EF,CD⊥EF,直线AB、EF、GH相交于一点,若∠1=40°,则∠2等于( )