一棵小树苗能长成一棵参天大树的奥秘是（） A．细胞的生长使_爱下问搜题

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问题选择题

一棵小树苗能长成一棵参天大树的奥秘是（）

A．细胞的生长使体积增大

B．细胞分裂使细胞的数量增多

C．细胞的分裂与细胞的生长共同作用

D．细胞的分化所致

答案

答案：C

题目分析：细胞分裂使细胞的数目增多，刚分裂形成的细胞体积小，细胞吸收营养又能不断长大，使细胞的体积不断长大。故一棵小树苗能长成一棵参天大树的奥秘是细胞的生长和细胞的分裂，二者缺一不可。故选项C符合题意。

问答题

在用焦距为10cm的凸透镜来探究成像规律的实验中，小吴将蜡烛、凸透镜、光屏依次放在光具座上，如图所示．

（1）点燃蜡烛后，在调整过程中，他发现光屏上承接蜡烛的像偏下，则应调整光屏、凸透镜或烛焰，使三者的中心大致在______．

（2）当蜡烛距凸透镜15cm时，移动光屏，可在光屏上得到一个清晰的倒立、______（选填“放大”或“缩小”）的______像．（选填“实”或“虚”）

（3）若遮住凸透镜的下半部分，则烛焰在光屏上的成像情况是______．（选填“完整的像”、“一半的像”或“无法成像”）

（4）若把图中的凸透镜看作眼睛的晶状体，光屏看作视网膜，给“眼睛”戴上远视眼镜，使烛焰在“视网膜”上成一清晰的像．若取下远视眼镜，则清晰的像会成在光屏的______（选填“前面”或“后面”）

完形填空

There was a small boy living on a farm which seemed like so far away from everywhere. He needed to get up before sunrise every morning to start his everyday jobs and go out again later in the evening to do the same 　36　.
During sunrise he would 　37　a break and climb up the fence so that he could see the house with golden windows 　38　 the distance. He thought 　39　 great it would be to live there and his 　40　 would wander to imagine the modern equipment and electric devices that might 　41　 in the house. “If they could 　42　 the golden windows, they 　43　 have other nice things.” He then 　44　 himself, “Some day I will go there and see that wonderful place.”
Then one morning his father told him to stay at home and he would do the everyday jobs. 　45　 that this was his chance, he packed a sandwich and　46　 the field towards the house with golden windows.
He walked and walked. As the afternoon went on, he began to realize how he misjudged the long 　47　 and something else was very wrong. As he 　48　 the house, he saw no golden windows but instead a place in bad 　49　 of a painting surrounded by a broken-down fence. He went to the tattered (破烂的) door and 　50　. A small boy very 　51　 his age opened the door.
He asked him if he had seen the house with 　52　 windows. The boy said “Sure, I know” and 　53　 him to sit on the porch (门廊). As he sat there, he looked back from 　54　 he just came; the sunset 　55　 the windows of his house to gold there.

A．satisfied with

B．familiar with