世界人口的地理分布很不均匀。读下图，可知世界人口集中分布在   (    )

2015年3月，全球最大的太阳能飞机“阳光动力2号”（如图所示）开始首次环球航行，途径我国重庆和南京两个城市，此行的重要目的是传播新能源理念。

（1）该机白天利用高效太阳能电池板将电磁能（太阳能）转化成电能；夜间飞行时，利用其超轻薄锂离子电池储备的　  　能转化成电能，首次实现昼夜飞行而不耗费一滴燃油。

（2）为降低飞行时的能量消耗，该机选用新型轻质材料．取面积为1平方米、厚度为1毫米的新型材料，测得其质量为250克，则该材料的密度为多少？

（3）该机计划从南京起飞后直飞美国夏威夷，是此次环球航行中最具挑战性的一段行程，飞行时间长达120小时．飞行过程中依靠平均功率为10千瓦的电动机提供动力，其消耗的能量全部由太阳能电池板吸收的太阳能提供，则此段航行中至少需吸收多少太阳能？（太阳能电池板的转化效率约为30%）

1+7=____

6-4=____

5+5=____

8-0=____

根据短文内容从A、B、C、D四个选项中选出能填入相应空格内的最佳答案。

    Wang Yani was born in 1975. Even as a baby she loved to draw. Her father was an 1. Yani wanted to be like him. So she tried to stand like her father as she painted, which made him laugh.

    One day, Yani painted lines on her father's painting. He got 2. At the time, she was only two and a half years old. She cried and said,“I want to 3 like you!” Her father looked at her without saying anything. He 4 remembered his childhood. He also wanted to draw and paint, but his parents didn't understand. They just got angry. He didn't want to see the same thing happen to his daughter. So he decided to 5 her.

    With her father's help, Yani soon 6. Her lines became flowers, trees, and animals. Her father took her to parks and zoos to get   7 for her paintings. By the end of six, Yani had made over 4,000 works. Her paintings were very special. People 8 her works. When she was eight, one of her paintings was made into a Chinese postage stamp.

    Yani became famous when she was young. Her works were 9 in different countries in Asia, Europe and North America, 10 her parents never sold her paintings. She is well-known to the world, and art is still a great joy in her life.