题目

已知R2+有b个中子，核外有a个电子，表示R原子符号正确的是（    ） A．R      B．R      C．R       D．R 答案：C 从方框中选择适当的句子，完成下面的对话。 W：Hi，Rita．Are you going to the school party tonight?     M：Sure! I'd love to．1．                             W：Me，too．And l want to bring my friend Jenny．She is good at singing and dance． M：2．                       W：What will happen if I do? M：3．                       ． W：What a pity! 4．                          M：You'd better not．I think．you should wear your cool pants． W：5．                       See you tomorrow． M：See you．