柴油机的经济性比汽油机经济性好的主要原因是柴油机的压缩比比汽油机的压缩比高。
参考答案：对
Great changes _____ in my hometown since 1980. [ ]
A. have been taken place
B. took place
C. have taken place
D. were taken place
同一组硬横跨两支柱基础中心连线应垂直于重要线线路中心，允许偏差不大于（）°。
A、1
B、2
C、3
D、4
