若C是AB的中点，D在线段AB上，且是AE的中点，若AB=15cm，DE=6cm，求CE的长．

①珍爱自己的生命       ②发挥自己的优势

③展现自己独特的风采   ④用自己喜欢的方式享受美好人生

在胰岛B细胞合成胰岛素的过程中，不需要（  ）

下图为某地貌形成演变图，形成该地貌的主要地质作用是（    ）

①水平挤压            ②变质作用

③外力作用            ④岩浆活动

阅读短文，判断正确还是错误。

A letter

Here is a letter from Jim to his friend in the USA

Dear Lily:

    I am in China now. I go to school five days a week. The school and the food are good here. I have some Chinese friends. They are all very friendly to me. On Saturdays and Sundays we stay at home. In the afternoon we play games. My Chinese friends like English very much. They ask me to teach them English and they teach me Chinese. I like staying here.

    Please write soon!