问题
选择题
—What time does your brother have to go to bed?
—________ nine o'clock. [ ]
A. By
B. On
C. In
D. With
答案
答案：A
搜题请搜索小程序“爱下问搜题”
—What time does your brother have to go to bed?
—________ nine o'clock. [ ]
A. By
B. On
C. In
D. With
答案：A
，其中n是正整数，求n和a的值。