为加粗词选出一个恰当的义项[ ]
假舟楫者，非能水也，而绝江河。
A．断，断绝
B．超越，超过
C．拒绝
D．横渡，横穿
答案：D
c≠0是方程 ax2+y2=c表示椭圆或双曲线的（ ）
A．充分不必要条件
B．必要不充分条件
C．充要条件
D．不充分不必要条件
—I hear the famous singer Xu Song may come to Ningbo next month.
—Really? _____ he comes, my younger sister will be very excited.[ ]
A. If
B. Until
C. Unless
D. Before
