By serving others，a person focuses on someone other than himself or herself，______ can be very eye­opening and rewarding.

A．who

B．which

C．what

D．that

在适宜温区内，昆虫的生命活动正常进行，因此，该温区又称为有效温区。在（）该温区内，昆虫体内能量消耗最小，死亡率最低，生殖力最强，但寿命不一定最长。

A、致死高温区

B、最适温区

C、适宜温区

D、致死低温区