Board logo

标题: 四级练习2015.06.30 [打印本页]

作者: Rebecca949    时间: 2015-7-3 10:41     标题: 四级练习2015.06.30

[audio]http://sound.yywz123.com/tingbbs/cet4/cet420150630.mp3[/audio]



You may not realize that fog is simply a cloud that touches the ground.Like any cloud (1)_______________,or in rare cases,of ice crystals that form an ice fog.Ice fogs usually occur only in extremely cold climates,because water droplets are so tiny (2)_______________,generally 30 degrees below zero Celsius or lower.The droplets of fogs are nearly spherical.The transparency of fog depends mainly on the concentration of droplets.The more droplets,the denser the fog is.(3)________________,investigators were puzzled for a long time as to why the water particles in fog didn't simply fall to the ground,making the fog disappear.It turns out the droplets do fall at a predictable rate,but in fog_creating conditions,they are either supported by rising air currents or continually replaced by new droplets condensing from the water vapor in the air.




本帖隐藏的内容需要回复才可以浏览





欢迎光临 英语听力论坛 (http://bbs.tingroom.com./) Powered by Discuz! 7.2