She can speak quite fluent English.She ____
问题描述：
She can speak quite fluent English.She ____
A.must be in the U.S.A.for some time
B.must have been in the U.S.A.for some time
C.should have been in the U.S.A.for some time
D.may be in the U.S.A.for some time
答
B为什么不是D表示肯定系数较大的一种推测。may 肯定系数较小。