— A computer is very popular and helpful . — I think so. It _______ in many different fields. A. used B. will use C. is used D. was used 答案:C 下列叙述中指定粒子的数目大于6.02×1023的是 ( )A.1.8 g水中含有的电子数B.0.1 mol F-中含有的电子数C.标准状况下,11.2 L H2和O2混合气体中的原子数D.1 mol Na2SO4中的Na+数