I wonder why Jack always gets good marks when he does only ______ the others. [ ]

A. half as much as

B. as much as half

C. half as many as

D. as many as half

秋季，晴朗的夜晚，农民点燃地里的秸秆，烟雾弥漫，据说能防霜冻，原因是烟雾（）

A.能减少大气逆辐射

B.能增加大气逆辐射

C.能使地面辐射减弱

D.能增加地面辐射