A.what
B.who
C.how
D.why
[单选题]How many people can live on the face of the earth? No one knows the answer.
[单选题]How many people can live on the face of the earth? No one knows the answer.
[单选题]How many people can live on the face of the earth? No one knows the answer.
[单选题]How many people can live on the face of the earth? No one knows the answer.
[单选题]How many people can live on the face of the earth? No one knows the answer.
[单选题]How many people can live on the face of the earth? No one knows the answer.
[单选题]How many people can live on the face of the earth? No one knows the answer.
[单选题]How many people can live on the face of the earth? No one knows the answer.
[单选题]How many people can live on the face of the earth? No one knows the answer.
[单选题]How many people can live on the face of the earth? No one knows the answer.