原料油特性因数越小，（）；用较低氢碳比的原料油可提高（）；芳构因数增加（）增加；相关指数越高，（）越高。
参考答案：收率越高；炭黑的收率；收率；收率
短文改错。
It is interesting to visit foreign country,but there 1.________
are some problems if we know the language very well. 2.________
It may be difficulty to talk with the people there. 3.________
We may don't know how to use the telephone there. 4.________
We may not know how to buy things we needs. 5.________
In a strange country,we may not know where to
be eat or what to order in a restaurant. 6.________
When we need help,we may not know how to ask help. 7.________
It was not a happy thing to have an experience like that. 8.________
常用木龙骨规格有哪些？（）
A．2cm×3cm
B．3cm×4cm
C．4cm×5cm
D．4cm×6cm
