某蔬菜大棚使用一种温度自动报警器，如图所示。在水银温度计里封入一段金属丝，当温度达到金属丝下端所指的温度时，电铃就响起来发出报警信号，请你说说它的工作原理。

According to traditional Cherokee beliefs, we are part of (1) . We don’t (2) with it and we’re not trying to (3) it. We are a part of the Great Life. And within the Great Life, there are three great Laws of Nature, which tell us how we have to live in (4) with everything else. The First Law of Nature is that you don’t take any life without real (5) . So we shouldn’t (6) needlessly. We believe everything is alive, including animals, plants and (7) . And so to us, taking the life of a plant is just as grave a 8() as taking the life of an animal. The Second Law is that everything we do should (9) the Great Life. And everything we do (10) the Great Life, and everything that (11) within the Great Life affects us. So it’s very important that what we do will not (12) other parts of the Great Life. The Third Law basically is that we don’t (13) where we live. And where we live is not our (14) , small community. It’s this (15) . We don’t pour chemical (16) down the drain because they all wind up in the water. It might seem a little difficult to live by those three laws in this (17) society. But there are still a lot of things that we can do to bring these laws into our lives, such as (18) , using the (19) as little as possible, and (20) gardening.