下列不是造成空气污染的原因是 [ ]
A.工厂烟囱冒出的浓烟
B.工厂排出的废水
C.机动车排出的尾气
D.人们生活用煤、柴排放的烟雾
答案:B
.-How about paying a visit to Mr. Richardson, our former history teacher?
-Good idea. I will e-mail him today so he ______ know ______ to expect us.
A.shall; why
B.may; when
C.would; why
D.will; how
A.a为动滑轮,B端钢缆受到滑轮组的拉力大小约为3G
B.a为动滑轮,B端钢缆受到滑轮组的拉力大小约为G
C.a、c为动滑轮,B端钢缆受到滑轮组的拉力大小约为3G
D.a、c为动滑轮,B端钢缆受到滑轮组的拉力大小约为G