煤的真相对密度是煤的主要化学性质之一。它在研究煤的煤化程度,选定煤在减灰时的重液分选密度时均要用到。
参考答案:错
We all feel_________the disabled girl has made so much progress in music. [ ]
A. worried
B. lovely
C. surprised
档案库只允许哪些人员进入?