以色列科学家利用胚胎干细胞成功培育出了心肌细胞．依据的原理主要是（    ）

两块大小、形状完全相同的金属平板平行放置，构成一平行板电容器，接通开关S，电源即给电容器充电（    ）

如图，Rt△APC的顶点A，P在反比例函数y＝$\frac{1}{x}$的图象上，已知P的坐标为（1，1），tanA=$\frac{1}{n}$（n≥2的自然数）；当n=2，3，4…2010时，A的横坐标相应为a₂，a₃，a₄，…，a₂₀₁₀，则$\frac{1}{a_2}$+$\frac{1}{a_3}$+$\frac{1}{a_4}$+…+$\frac{1}{a_{2010}}$=（　)

黄老师在介绍我国古代某一朝代市民生活的讲解中多次提到瓦肆（瓦子），由此推断，这一朝代应是（　　）

    Australia is the smallest continent in the world. It is a little smaller than China. It is on the Southern Hemisphere of the earth. Australia is big, but its population is small. The population of Australia is nearly as large as that of Shanghai.

    Enough laws have been made to fight against pollution. The cities in Australia have little air or water pollution. The sky is blue and the water is clean. You can clearly see fish in the rivers. Plants grow very well.

    Last month we visited Perth, the biggest city in Western Australia, and went to a wild flower exhibition. There we saw large numbers of wild flowers on show, most of which we had never seen before. We had a wonderful time. Perth is famous for its beautiful wild flowers. Every year in spring Perth has a wild flower exhibition. After visiting Perth, we spent a day in the countryside. We sat down and had a rest near a path at the foot of a hill. It was quiet and we enjoyed ourselves very much. When we heard bells ringing at the top of the hills, we looked up, but what we saw made us pick up all our things and run back to our car as quickly as we could. There were about three hundred sheep coming towards us along the path.

    Australia is famous for its sheep and kangaroos. After a short drive from any town, you will find yourself among the white sheep. Sheep, sheep, everywhere you can see sheep.