Here are summer activities in museums.

The Postal Museum

Date: July 16 to July 22

Age: 11—13

    Would you like to join us this summer vacation? You can learn about the history of stamps (邮票)and design (设计) a stamp yourself. You can also enjoy many beautiful pictures in our museum.

Tel: 965-0403

The Air and Space Museum

Date: July 24 to July 30

Age: 8—11

    If you like activities about air and space, please come here. It's a good place to make and fly your own paper plane, watch an IMAX movie, and climb into a real plane.

Tel: 654-0937

The Science Museum

Date: August 7 to August 13

Age: 9-12

    You can experience video arts, play computer games about future cities, and ask robots questions here. It will be wonderful! Have fun!

Tel: 357-3039

The Building Museum

Date: August 15 to August 22

Age: 13-15

    Want to enjoy design challenges (挑战)? Come and join us. You can go on trips to some famous buildings, learn to design your own room, and build small houses,

Tel: 272-0561

根据材料内容选择最佳答案。

There are two____(国际的)airports in this city．

小明同学在学习了声现象后，总结了以下四点，其中说法错误的是（　　）

两个相似三角形的面积比为1∶4，那么这两个三角形的周长比为（     ）

有一列数a₁，a₂，a₃，…，a_n，满足下列条件：a₁=0，|a₂|=|a₁+1|，|a₃|=|a₂+1|，…，|a_n|=|a_n﹣1+1|．

求证：a₁，a₂，a₃，…，a_n这n个数的算术平均数不小于-$\frac{1}{2}$．