—Excuse me, sir, visiting hours are over. You leave.
—Pardon me, nurse. I didn't hear the bell.
A:may
B:can
C:must
D:need
先看一看每个字的间架结构,再写一写。
孙 挑 疼 痛 罪 宗
计算:(3.9×5.5×6.3×3.6)÷(1×3×5×7×0.9×1.1×1.3)=____ .
抛物线y=x2上的任意一点到直线x-y-2=0的最短距离为( )