在“验证凸透镜成像规律”的实验中，小明设计的实验报告（部分）如下，请填写空格处的内容．实验目的：验证凸透镜成像规律．实验器材：凸透镜、光屏、______、蜡烛和火柴等

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
Being a good student doesn’t mean you have to drop all social activities and dive into your books．It is still possible to have a healthy social life while getting good grades． 【小题1】 ．Here is how you can achieve it:
Decide for yourself at the start of the term that you won’t let your schoolwork sweep you away． 【小题2】
Write down your weekly schedule on a piece of paper．Chances are , you’ll have small gaps between classes during the week and more free time at the weekend．Make sure that every time you find yourself in one of those between-class gaps you use the time efficiently ．_【小题3】 ．
Set aside at least one large amount of time each week as free time．Keep in mind the law of diminishing returns （收益递减）．Past a certain point more hours studying will be of little benefit．_【小题4】 ．Protect both your free time and your school time carefully ．If one starts to infringe （侵犯） on the other that is just the beginning of a long, slippery downhill slope （斜坡）．
【小题5】 ．This way, you can co-ordinate（协调） your free time with theirs．
Whenever possible, find social activities that take you off campus and away from your schoolwork．A．Balance is the key ．B．Encourage your friends to follow a similar plan．C．It is very important to be determined about this．D．Try not to affect other’s time and just focus on your own． E．You’re better off spending this time with friends．
F．You can spend more time on social life than on study．
G．Read a few pages of your school book or do some quick chores（杂活）,for example．A

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解：凸透镜成像实验的实验器材包括凸透镜、光屏、刻度尺、光具座、蜡烛和火柴等．实验前先测凸透镜的焦距．实验时，使烛焰的焰心，凸透镜的光心，光屏的中心，三者位于同一高度．固定好凸透镜和蜡烛的位置，然后移动光屏找像．
实验中，利用凸透镜对光线有会聚作用，可得焦距．测焦距时要估读到分度值的下一位．物距大于2倍焦距成倒立、缩小实像．近视镜是凹透镜对光线有发散作用，近视眼镜能使像相对于晶状体向后移，所以光屏应远离凸透镜．