渣油生产氨成本较低。
参考答案:错
解析:渣油生产氨成本较高。
I couldn't do my homework with all that noise _____. [ ]
A. going on
B. goes on
C. went on
D. to go on
活塞顶是燃烧室的一部分,活塞头部主要用来安装活塞环,活塞裙部可起导向作用。