Having a large family to support, Mr.Johnson had to work     in the evening.

A．four another hours.

B．more four hours.

C．other four hours.

D．four extra hours.

大样本资料，估计总体率的可信区间可用

A．查表法

B．正态近似法

C．对数正态法

D．百分位数法

E．直接计算概率法