I'm going ____________ the stairs. [ ]
A. to
B. in
C. too
答案：A
有一个正方形的操场，每边都要种15棵树，而且四个角上都要种一棵，这个操场的四周一共要种多少棵树？
— Sorry indeed, I ______ to your birthday party if…
— Forget it. I know you were out on business. [ ]
A. must come
B. would have come
C. must have come
D. would come
