生物对()的耐受性范围称为生态幅。
参考答案:生态因子
--- __________ do you chat by QQ with your friend in Shanghai every week?
--- Two hours. I have much homework to do every day.
A.How often
B.How long
C.How far
D.How soon
烟道挡板的作用是()
A、控制通风量
B、调整炉出口温度
C、控制瓦斯消耗量