质点
参考答案：
忽略大小、形状和内部结构而视为几何点的物体。
The Chinese government is trying to do something to _____ better understanding between the two countries.[ ]
A. widen
B. increase
C. raise
D. promote
柴油机运行（）后，应清洗检验一次喷油器。
A.200h
B.225h
C.250h
D.275h
