城市公共场所如公园、街道、体育场、绿化带清扫废弃物等统称为（）。
A.危险垃圾
B.建筑垃圾
C.生活垃圾
D.清扫垃圾
参考答案：D
— What are the _______ doing there?
— They are busy _______ their science experiment.
A．Boys students; to do
B．Boy students; to do
C．Boys students; doing
D．Boy students; doing
航天飞机在飞行过程中完全不依靠航空原理。
