题目

E-mail, as well as telephones, _____ an important part in daily communication.    A. are playing         B. play          C. is playing       D. have played 答案：C下列各表中的数字代表的是原子序数，表中数字所表示的元素与它们在元素周期表中的位置相符的是 [     ]A．B．C．D．