氧熔剂切割
参考答案:
氧熔剂切割是在切割氧流中加入纯铁粉或其它熔剂,利用它们的燃烧热和废渣作用实现气割的方法为氧熔剂切割。
单句改错(共5小题,每小题1分,共 5分。每句只能改一处,在原句中直接改正)
小题1:Air hostesses all smile when they serve for the passengers.
小题2:No one matches him when it comes to swim.
小题3:A poor nourished body needs more energy to combat disease.
小题4:Foreigners always associate China to the Great Wall.
小题5:Not until then he realize the importance of the problem.
________是生物圈中的生产者,生物圈中的动物必须直接或间接地以________为食。