but when they cross a busy road_using__a crosswalk,traffic is held up.为什么用using.求详细解释!

when they walk ()the desert they find nothing but some water为什么不能填cross? but when they cross a busy road_using__a crosswalk,traffic is held up.为什么用using.求详细解释! but they are very easy when you( )them 填词 children should avoid _____ hurt when they cross the road being be to be been 选哪个? when we put on them,they are full.but they are empty when we dont use them.what are they? 一、用所给动词的适当形式填空.Jim,together with his classmates,______(play) table tennis now.Last Sunday morning,i did noting but ______(write) a letter to my grandma.When the traffic ______(stop),you can cross the road.They needed _____ Sofa is made of ___.They are fiying kites ____ in the gentle breeze.Don't cross the road when the traffic lights are red.____ _____ cross the road when the traffic lights are red BRITS pride themselves on being pragmatic,but when it comes to banks they are anything but. Cross the road.Walkquickly,but don'run. When I cross,it's over Be_____(care)when you cross the street. The students cross the river on a ropewayThe students cross the river on a ropeway every day,but they aren't（ ） A.quick B.gets C.leaves D.comes show that they could cross the road you should look （） first in china when you cross the road,but in england,（）firstA.right,leftB.left,leftC.left,rightD.right,right -look!there____lots of traffic in this day .-_____we should be careful when we cross the street.A.are;but B.is;so为什么不用are而用is 连词成句.1、do don't exercises they here morning2、cross shouldn't you the road light when is the red 每一个人都必须细心,当他们横路时.Everyboby＿＿＿ ＿＿＿ ＿＿＿When they cross the road. people used to carry ___bags when they went shopping but now they but now they use clothbags insteadA fresh Bnatural C plastic D harmful