单项选择题
A.4 B.5 C.6 D.7
A.10% B.20% C.30% D.40%
A.30% B.50% C.60% D.80%
A.20 B.30 C.40 D.50
A.10 B.20 C.30 D.40
A.40% B.30% C.60% D.70%
A.10%-30% B.30%-80% C.45%-65% D.60%-80%