他一天到______坐在电脑前，也不知在忙个啥。
A．早
B．晚
C．头
D．完
参考答案：B
I really appreciate ______ to help me with my maths, but I'm afraid that I have no time this week. [ ]
A. you to offer
B. it you offer
C. your offering
D. this you are offering
在一个无向图中，所有顶点的度数之和等于所有边数的多少倍
A．3
B．2
C．1
D．1/2
