①y=f（x）的最大值为 $\sqrt{2}$ ；

②y=f（x）最小正周期是π；

③y=f（x）在区间 $\frac{\pi }{24},\frac{13\pi }{24}$ 上是减函数；

④将函数y= $\sqrt{2}$ cos2x的图象向右平移 $\frac{\pi }{24}$ 个单位后，将与已知函数的图象重合．

其中正确命题的序号是____．

⑴What's your favourite season?____                           A. It's sunny and cool.

⑵Why do you like winter?____                                    B. I can swim.

⑶I like spring.____                                                       C. Autumn.

⑷What can you do in summer?____                           D. Because I can skate.

⑸What's the weather like in autumn in Beijing?____  E. Me too.

以下哪两点所连成的直线被称为中国的人口地理界线（　　）

河西走廊降水____气候____，气温年较差较大，属于____气候。