正确答案: B

大于焦距，小于2倍焦距

题目：放在凸透镜前10厘米高的蜡烛，通过凸透镜折射以后成的像高15厘米，则物距的范围在（ ）

解析：B

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学习资料的答案和解析：

[单选题]5． You're too tired． You should __________for a few days．

lie down

[单选题]3． _______the Great Green Wall，the land produces more crops

．

Thanks to

[单选题]15．

idea

解析：15.B【解析】work“工作”，idea“想法”．box“箱子”。这应该是那位妻子的想法。

[单选题]The Whites live in a small village． They have (11) small farm and they work there every day．They have a son， John． He is (12) ．He lives with them，(13) he doesn’t like to work in the village． He (14) to work in a city． He can (15) the gui-tar， and he can play it (16) ．Then he gets a job ( 17) a city．He (18)an art club．John likes his new work (19) ．He is very(20) ．( )11．

a

[单选题]下面各角能成为某多边形的内角和的是（ ）

4320° -