原煤可选性是指通过分选可改善煤的()的可处理性。
A、重量
B、矢量
C、质量
D、产量
参考答案:C
So suddenly ________ that people had no time to escape. [ ]
A. did the earthquake happen
B. the earthquake happened
C. was the earthquake happened
D. the earthquake was happened
“影响使用功能和工程结构安全,造成永久质量缺陷”的质量事故,是认定( )的一个条件。
A.一般质量事故B.严重质量事故C.一级重大质量事故D.四级重大质量事故