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
He started to walk faster and the children had to run to ________him.
A.come up with
B.catch up with
C.keep up with
D.put up with
哪些是我国允许使用的抗氧化剂
A.二氧化硫B.糖精C.山梨酸D.亚硝酸钠E.异山梨酸钠