题目

Which sentence can we put in the blank? Beijing, Shanghai, Nanjing and other big cities are good places to live in. You can visit different museums and places of interest. You can also buy things from all over the country. A . Many people like living in big cities. B . There are many problems in big cities. C . Many people move to the cities to find jobs. D . There're many interesting things to see and to do.下列各对原子序数的原子能以共价键结合成化合物的是A.9和11B.6和1C.11和1D.12和17