室内空气质量标准规定，对于100m2的房间采样点最少应设置的数目为（）
A.1个
B.2个
C.3个
D.4个
E.5个
参考答案：C
Large quantities of water, as well as some other timely help including a medical team ___since the serious drought hit Yunnan Province.
A．has offered
B．had been offered
C．have been offered
D．is offered
采暖系统按所用热媒不同，可分为( )。 ①支管散热系统；②热水采暖系统；③蒸气采暖系统；④热风采暖系统；
A．①②③
B．②③④
C．①②④
D．①③④
