【单选题】How many categories are hotels divided into by the rank of stars ?
【单选题】How many categories does the writer classify into?
A.
There are two categories.
B.
There are three categories.
【单选题】膨胀阀的作用是( )
A.
将低温低压气态制冷剂转化为低温高压液态制冷剂
B.
将低温高压气态制冷剂转化为低温低压液态制冷剂
C.
将低温高压液态制冷剂转化为低温低压液态制冷剂
D.
将高温高压气态制冷剂转化为中温低压液态制冷剂
【简答题】The two categories of crystalimperfections are A) ______ and B) ______