下列哪项条件不属于二氧化硫控制区划分的基本条件。( )

A．近年来环境空气二氧化硫年平均浓度超过国家二级标准

B．日平均浓度超过国家三级标准

C．小时浓度超过国家三级标准

D．二氧化硫排放量较大

The man called his professor for help because he couldn’t solve the problem by _________.

A．herself

B．himself

C．yourself

D．themselves