振动筛的筛分质量不好，可能原因是（）
A、筛孔堵塞
B、原料水分高
C、筛网不紧
D、以上都是
参考答案：D
He looks very sad because someone _______ his home and took away his computer last night. [ ]
A. broke out
B. broke up
C. broke off
D. broke into
煤的水分是指单位质量煤中水的含量，它包括（）和（）。
