运行中煤的挥发分和六分增大时，输煤系统应注意做好（）的措施。
A、防尘
B、防自流
C、防自燃
D、防爆
参考答案：C,D
Before the final examination, many students have shown ____ of tension. Some have trouble in
sleeping while others have lost their appetite. [ ]
A. anxiety
B. marks
C. signs
D. remarks
无足型幼虫
