合成系统空速越大，气体与催化剂的接触时间越短，氨的转化率就越低，氨净值越小。
参考答案：对
——So you are not spending your holiday in Wuhan this year.
——No, ____.
A．everywhere in Wuhan
B．somewhere in Wuhan
C．somewhere but in Wuhan
D．anywhere but in Wuhan
起重桅杆的安装方法有哪几种？
