You ______ be polite to the old man. [ ]
A. should
B. can't
C. might
D. mustn't
答案:A
一个角有( )条边。
设i,j,k均为int型变量,则执行完for(i=0,j=10;i<=j;i++,j--)k=i+j;语句后,k的值为【 】。