已知:①气态链烃A在标准状况下的密度为1.875g·L-1;
看图读一读填空,把句子代码填在正确的横线上。
A. There's a blackboard in it. There are eighteen desks and eighteen chairs in it.
B. There are three books in it. C. There's a ruler. D. There's a big library.
托盘天平的横梁上都有标尺和游码,移动游码的作用是( )。