定义在R上的函数y=f(x)满足f(x+6）=f(x)，当$-3\le x<-1$时，$f\left(x\right)=-(x+2{)}^2$，当$-1\le x<3$时，$f\left(x\right)=x$则$f\left(1\right)+f\left(2\right)+f\left(3\right)+\cdots +f\left(2012\right)=$ （     ）

实验室常用温度计一般有水银温度计和酒精温度计，它们根据 ____原理制成的．

在下列现象中，属于用热传递方式改变物体内能的是（　　）

（Jeff and Li Lei are talking on the phone now. Jeff=J Li Lei= L）

J: Hello, Li Lei?____.

L: Hi, Jeff. Are you still in Beijing?

J: Yes.

L: Well, ____?

J: I'm studying English here.

L: How's it going?

J: ____. I'm having a good time. It's interesting to talk with the foreigners(外国人）.

L: ____?

J: Sunny and warm! Do you want to come to Beijing this summer vacation?

L: Yes, but I am busy now. Could you take some photos of Beijing?

J: ____! Er, er. Are you studying for a test now?

L: Yes, I don't think the test is easy. I must study hard!

J: Good luck!

L: Thank you!