His father got him a job in a bank but soon it became clear          he was not fit for that kind of work．

A．why

B．what

C．whether

D．that

将调查总体各单位的名称或号码逐个写在签条或卡片上，放在箱中，打乱次序，拌和均匀，然后按抽签办法，不加任何选择地在全部签条或卡片中随机抽出所需的调查样本，这是（）。

A、抽签法

B、随机数表法

C、分层随机抽样

D、分群随机抽样法