题目

The father went to the bookstore to ________ a reference book for his son. A. choose                               B. elect C. appoint                              D. select 答案：D已知14.2g X气体在标准状况下的体积是4.48L，则X气体的摩尔质量是 ( )A．71g B．71 C．71g /mol D．142g /mol