凡工程质量不合格,必须进行返修、加固或报废处理,由此造成直接经济损失低于5000元的,称为( )。
A.质量不合格
B.质量问题
C.质量缺陷
D.质量事故
参考答案:B
Our playground is not so tidy and beautiful as before. Students must _____ dirty things on it. [ ]
A. be stopped to throw
B. be stopped from throwing
C. stop to throw
D. stop from throwing
瓦斯继电器装在变压器()和()之间的联接管道中。