贮煤场中煤发生自燃的主要原因是（）。
A.煤中挥发份含量太高
B.煤中含碳量的高低
C.空气中氧的作用
参考答案：C
临床表现以门脉高压为主，肝功损害轻的肝硬化是
A．大结节性肝硬化B．小结节性肝硬化C．混合性肝硬化D．不完全分隔性肝硬化(如血吸虫肝纤维化)E．胆汁性肝硬化
The teacher was a little angry because the students didn't _____ their exercise books on time. [ ]
A. hand out
B. hand to
C. hand in
D. hand on
