排粉机内部流动的介质是（）
A.空气
B.煤粉
C.空气或者煤粉和空气的混合物
D.煤粉和空气的混合物
参考答案：C
—Jim can't go hiking with us, he has a fever and lies in bed.
—_____[ ]
A. I'm sorry to hear that.
B. Really?
C. Why?
D. Great!
在资产证券化过程中发行的以资产证为基础的证券称为证券化产品。 ( )
