It is time now to learn ________ to protect our atmosphere, the roof over the world of man.
A. what
B. which
C. how
D. that

A.可以不按照他们的先后顺序，对其中任何一人、数人或者全体行使追索权
B.必须按照他们的先后顺序行使追索权
C.必须同时对他们全体行使追索权
D.只能选择其中一人行使追索权

A.对
B.错

A.2002-6-25
B.2002-9-1
C.1992-4-15
D.2002-3-26