用括号内所给动词的适当形式填空。
(1)In the past three years, my home town ____ (change) a lot. already.
(2)It's hard to say what____  (happen) in 100 years in our country.
(3)They____ (not travel)to Shanghai next week, are they?
(4)The students____ (chat) from 6 to7 yesterday evening.
(5)When I got to the station yesterday morning, my friends____ (wait ) for me at the entrance.
(6)If it____  (not rain) tomorrow, we’ll go hiking.
(7)He____  (not write) a letter to his mother yet. He has to do that soon. His mother misses him very much.
(8)Would you please____ (not make) such a big noise. The baby is sleeping.
(9)It's a long time since we ____ (meet) last time, isn't it?
(10)How many times____ the girl____ (forget) to take the keys to her home?
    At least three times.
(11)You must spend as much time as you can ____ (practise) playing the piano.
(12)They____ (live) in Wuxi since they were born.

①背景：七七事变的爆发

②主张：停止内战，一致抗日

③地点：陕西西安

④意义：抗日民族统一战线正式建立。