— What did the farmer do ________the farm?

— He_______ the chickens.

                    彩虹

    彩虹是大气中一种光学现象，当阳光照射都半空中的水珠时，光线被折射和反射，在天空形成彩带．

    研究光线经过水珠的传播规律，可揭示彩虹形成的原因，如图甲所示，光线从点C进入半径为R的水珠，经点D反射，再从点E射出，AB是通过水珠球心O且与入射太阳光平行的直线，用x表示进入水珠的光线距AB的距离，α表示射出光线与AB的夹角，画出过入射点和球心O的直线（即该入射点的法线），进一步研究可以得出α与x的关系如图乙所示，入射的太阳光分布是均匀的，但射出的光线分布是不均匀的，在α最大时强度最大，能被地面上的人观察到．

    牛顿发现，太阳光通过三棱镜后被分解成七种单色光．当太阳光进入水珠时，也产生类似效果．从同一点进入水珠的不同色光在水珠中沿不同路径传播，致使不同色光的α的最大值略有不同．

    由于不同色光的α最大值略有不同，对某一水珠来讲只能有一种颜色的光被地面上的人看到，进入人眼的不同颜色的光来自内外不同弧线的水珠，所以人眼看到的彩虹由外圈至内圈呈红、橙、黄、绿、蓝、靛、紫七色．

    One day after school I was just finishing up some math homework. My dad came back from work and sat right beside me1over my homework with me. We made corrections 2 After that we3and my dad said,＂ I will always4every moment spending time talking with you.＂

    I remember my Dad telling me his stories of when he was 5My dad didn't have a father6He was always moving from place to place with my 7My dad wasn't the easiest kid to 8He would 9with kids at school, which made my grandma worried. He'd act out to release the anger he had from not having his father present in his10and teenage years.

    At high school, things got a little 11 He made a football team, he did well and didn't get into as much 12as before. He also made many friends13those friends was my uncle. My Dad and Uncle were friends all throughout high school. It was through my uncle14my Mom and Dad met15Later, they got married. After I was born, my dad felt that becoming a 16was an honor and that he would not be17in my life.

    I suddenly looked up to see my Dad18at me. I could see in my Dad's eyes how he longed for a19 like this. I continued to do my math homework and20my Dad say,＂ I love you, always.＂

2000年，我国人口总数为12亿9千5百万人，用科学记数法表示我国人口总数（   ）

如图所示，用方向不变的力F，将杠杆从A位置匀速提升到B位置的过程中，F的大小变化情况有（　　）