眼球内有感光细胞的结构是（） A．角膜 B．虹膜 C．_爱下问搜题

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问题选择题

眼球内有感光细胞的结构是（　　）

A．角膜

B．虹膜

C．巩膜

D．视网膜

答案

眼是人的视觉器官，其主要结构是眼球，眼球有许多结构．

A、角膜是无色透明的，能够使光线通过，但没有感光细胞，故不符合题意．

B、虹膜里面有色素，是眼睛中的黑眼球，没有感光细胞，故不符合题意．

C、巩膜是白色、坚韧，有保护作用，是眼睛中的白眼球，没有感光细胞，故不符合题意．

D、视网膜分布着感光细胞，能形成物像，故符合题意．

故选：D

填空题

罗马万神庙的穹窿体象征着（）。

完形填空

完形填空。
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