题目

补全对话（有两项多余）A:You must be really excited about leaving for America tomorrow, Li Ping. B:Yeah. A:Nervous about what? B:I don't know any of the customs and manners in the USA. A:Sure. B:A: Well, it's important to beon time when you're invited to dinner. Americans expect their gueststo be on time.B:Then how long may I stay there? A:Or you seem to come only for the meal. When your friends seem to begetting tired and running out of things, it's time to leave. The next day, callor write a thank-you note to say how much you enjoyed the evening. A. It's good for you to stay a19．现有一种金属R（可能是银、镁、铁中的一种）．欲确定R，请你一起完成：（1）取少量的金属R的粉末于试管中，逐滴加入稀硫酸，有气泡产生，则R不可能是银．（2）待不再产生气泡时，再往溶液中加入洁净的锌片，锌片表面有金属析出，写出锌片表面析出金属R的化学反应方程式Zn+FeSO4=ZnSO4+Fe．