人眼的结构如图所示，近年来时兴一种角膜切割手术治疗近视眼使患_爱下问搜题

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人眼的结构如图所示，近年来时兴一种角膜切割手术治疗近视眼使患者抛弃眼镜，以下说法正确的是

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A．用激光切割近视眼角膜，使之周围变薄相当于人造凸透镜替代镜片

B．矫正远视眼应让患者戴上凹透镜

C．用激光切割近视眼角膜，使之中央变薄相当于人造凹透镜替代镜片

D．玻璃体相当于一个焦距可变的凸透镜

答案

答案：C

问答题简答题

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Peter and Paul had got permission from their parents to camp in a field close to their farm.But,being adventurous boys,they knew it would be more 1 to camp in the woods that lay beyond the river.Excitedly,the boys 2 with their tent and food. Carrying their heavy 3 ,the two brothers walked along the riverbank,hardly noticing the distance or the sun beating down.They were eager to reach their 4 before lunchtime. As they entered the cool,shadowy woods,they began to search for a suitable camping spot. Peter wanted to 5 close to the river at the edge of the woods, 6 Paul,who was older, insisted that they camp further away. 7 ,Peter followed his brother deeper into the 8 . "This really is a wonderful setting!" said Paul in excitement.They 9 their tent,and settled down to eat the sandwiches they had made,then decided to find their way 10 to the river to catch some fish. "Are you sure that this is the right 11 ?" whispered Peter shakily."I'm sure we passed that hollow tree just a while ago." Paul walked 12 silently."Look,there it is again.We're lost,aren't we?" complained Peter.Paul had to admit that he didn't know where they were. 13 ,they were a long distance from where they were 14 to be.They were not even 15 of where they had set up their camp.They set in 16 for a few minutes until Peter had a bright idea."Why don't we look for clues(线索)the way that trackers 17 in the movies?We weren't careful about how we walked,so I'm sure we would have left 18 some broken tree branches and leaves." Carefully,the boys 19 the marks that they had left,until finally they found their campsite. Hurriedly,they packed their belongings and set off 20 the direction of the river. What would their parents think of their adventure?
( )1.A.surprising ( )2.A.went round ( )3.A.load ( )4.A.grassland ( )5.A.live ( )6.A.but ( )7.A.Unconsciously ( )8.A.woods ( )9.A.put off ( )10.A.forward ( )11.A.place ( )12.A.alone ( )13.A.After all ( )14.A.discovered ( )15.A.afraid ( )16.A.enjoyment ( )17.A.appear ( )18.A.behind ( )19.A.fetched ( )20.A.for	B.exciting B.went back B.tent B.destination B.lie B.and B.Unfortunately B.farm B.put on B.near B.mark B.about B.At last B.encouraged B.sure B.satisfaction B.do B.out B.watched B.to	C.annoying C.went away C.food C.field C.wait C.or C.Unwillingly C.setting C.put down C.back C.way C.in C.Above all C.persuaded C.informed C.disappointment C.work C.aside C.followed C.at	D.frightening D.went through D.storage D.river D.stay D.so D.Uninterestingly D.camp D.put up D.further D.time D.on D.At first D.supposed D.reminded D.imagination D.behave D.around D.collected D.in