—What do you think of this jacket?

—Well, I like its color, but the price is a little bit too ______. I don't think I can afford it. [ ]

A. cheap

B. low

C. expensive

D. high

热处理加热炉按炉膛内的加热介质不同分类，可分为空气炉、（）炉、（）炉和真空炉四种。