What will the weather be like? Some people say they can know what the weather will be like from birds. When they see birds fly high out to the sea , they know it is a nice day, because birds don't like to fly out when it will rain. When the weather will be bad, the birds come back to the beach. A big wind may come with a rain. Birds do not like to fly in a big wind. They may sit in a tree when rain is coming. Other animals can also tell the weather. It's a cloudy day. The rain is coming. Chickens aren't quiet, and they are running here and there. Frogs(青蛙) are making big noise in the pool. If it is a nice day, the frogs will come out of the water.

①细胞的分化、衰老和癌变对于生物体都是有积极意义的 

②高度分化后的细胞遗传物质发生了改变 

③细胞的衰老与机体的衰老总是同步进行的 

④衰老细胞膜的通透性改变，有利于物质运输 

⑤有些病毒能诱发人的细胞癌变

⑥细胞癌变主要是因为原癌基因和抑癌基因发生突变

⑦癌细胞比正常细胞分裂周期长

太阳能热水器具有安全、节能、经济和环保等优点．太阳能是一种 ____能源（选填“可再生”或“不可再生”）；某太阳能热水器水箱里盛有50kg、20℃的水，若水吸收了1.89×10⁷J的热量，水温将升高 ____℃在1标准大气压下，水的比热容为4.2×10³J/（kg•℃）．