在有n个结点的二叉链表中，值为非空的链域的个数为 ______。
A．n-1
B．2n-1
C．n+1
D．2n+1
参考答案：A
在“用单摆测定重力加速度”的实验中，下列所给器材中，选用哪些器材较好①长1 m左右的细线 ②长30 m左右的细线 ③直径2 cm的塑料球 ④直径2 cm的铁球 ⑤秒表 ⑥时钟 ⑦最小刻度是cm的直尺 ⑧最小刻度是mm的直尺[ ]
A．①③⑤⑦
B．①④⑤⑧
C．②④⑥⑦
D．②③⑤⑦
The children vary considerably in the rate at which they learn these lessons. ____, we make the teaching
plans different accordingly. [ ]
A. Because of this reason
B. It is because
C. As a result of
D. For this reason
．①③⑤⑦