确定提问方式时应把握的要点中不正确的是（ ）。 A．特殊情况下使用半开放式提问 B．

下列属于后天性行为的是（　　）

A．蜘蛛结网

B．母鸡育雏

C．春蚕吐丝

D．狗拉雪撬

Not until his father died ____ what his father really meant. [ ]

A. do they realize

B. did they realize

C. realized they

D. had they realized

在关系模型中，把数据看成一个二维表，每一个二维表称为一个【 】。

SW₆系列断路器的传动系统由水平拉杆、传动拉杆、提升杆和中间传动机构组成。

行车基本闭塞法采用哪几种？