请以“阳光下”为题写一篇作文。
         要求：①写出自己的真情实感。②文中不得出现真实的校名、人名。③写成记叙文，字数不少于600字。

A : What's your favourite invention?

B : Of course computers. They are very important in people's life now.       

A: I like computers, too. I think they will be used even more widely in the future.

B: I agree with you.        

A: I usually use my computer for looking up information reading books and playing games;

B: Do you like shopping online?

A : Yes, of course.       

B: That's true. However, sometimes it isn't safe to buy things online.

A: Yes, so we should be careful when shopping online. What do you like to do with your computer?

B:        

A: You must have many net friends.

B: Sure. I have about 10 friends who are from different countries.

A:        

若式子$\sqrt{x-3}$在实数范围内有意义，则x的取值范围是（　　）

在“比较不同物质吸热升温情况”的实验中：