一列沿x轴正向传播的简谐横波，在某时刻的波形图如图所示．a、b、c、d为介质中沿波的传播方向上的四个质点，在a、b、c、d四个点中，此时振动速度最大、且方向沿+y方向的点是（　　）

A．质点a

B．质点b

C．质点c

D．质点d

用所给词的正确形式填空。

1. I            (think) good friends should help each other.

2. My father is             (athletic) than my uncle.

3. There are so many           (different)  between the two dictionaries.    

4. My little brother is a shy boy.  He is         _(quiet) than me.

5. Would you like             (go) to the movies with me tonight?