题目

America’s first transcontinental railroad, completed 150 years ago today at Promontory Summit in Utah, connected the vast United States and brought America into the modern age. Chinese immigrants contributed greatly to this notable achievement, but the historical accounts that followed often ignored their role.Between 1863 and 1869, as many as 20,000 Chinese workers helped build the dangerous western part of the railroad, a winding ribbon of track known as the Central Pacific. At first, the Central Pacific Railroad’s directors wanted a whites-only workforce. When not enough white men signe某学生用KMnO4制O2收集到他所需要的氧气后停止加热，KMnO4未完全分解．剩余的固体混合物中锰元素与氧元素的质量比不可能是 [　　] A．55∶55B．55∶58 C．55∶62D．55∶64