Lookupinthesky．Doyouseeanyclouds？Whatdotheylooklike？Somecloudsarewhite．Othersareblack，andmakeyoutakeanumbrella．Whenthesunrisesorsets，cloudscanlookred，purple，oryellow-asiftheywerecolored．Butwhat

　　Look up in the sky．Do you see any clouds？What do they look like？Some clouds are white．Others are black，and make you take an umbrella．When the sun rises or sets，clouds can look red，purple，or yellow-as if they were colored．But what clouds anyway？You can't touch the clouds，but you can make your own in a jar（罐子）

　　You need：

　　●hot water●a huge，empty glass jar●ice cubes（小冰块）●metal strainer（过滤器）

　　Do the following：

　　Step1．Fill the jar with hot water，leave it there for two minutes，and then pour out most of the water，leaving just a little in the jar．

　　Step2：Put the strainer over the jar．Fill the strainer with ice cubes．Watch the jar．

　　What will happen？

　　A cloud forms in the jar!Some of the hot water in the jar turns into water vapor（水蒸气）．The water vapor rises and meets the cold air coming off the ice cubes．When the water vapor condenses，it forms a cloud．

　　Hot air rises and carries lots of water vapor with it．The higher the air rises，the more it cools down．Soon the cold air can't hold all the water vapor so it starts turning into tiny water drops，and becomes a cloud．

　　54．what's the passage mainly about？___

　　A．The size of clouds

　　B．The color of clouds

　　C．What makes a cloud

　　D．what happens when there is a cloud

　　55．What should we do right away after we pour most of the hot water out of the jar？___

　　A．Watch the jar

　　B．Fill the jar with cold water

　　C．Fill the strainer with ice cubes

　　D．Put the strainer over the jar

　　56．Where can we most probably read this passage？___

　　A．In a sports newspaper

　　B．In a science magazine

　　C．In a fashion magazine

　　D．In a guidebook．