阅读材料回答问题：

材料一：“贞观十五年，太宗以文成公主妻之，会礼部尚书、江夏郡王（李）道宗珠婚。持节送公主入蕃。弄赞率其兵次柏海，亲迎于河源。”——《旧唐书》

材料二：下图

材料三：2008年3月14日开始，我国西藏、四川、青海等藏族聚居区先后发生了多起打、砸、抢、烧暴乱事件，给人们的生命和财产造成了严重损失。“这起事件完全是由达赖集团有组织、有预谋、精心策划煽动起来的。”几十年来，达赖集团在反动势力和藏独分子的支持下，从事了大量的分裂祖国的活动。

— Why do you look sad?

— There are so many problems _____.

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。