一个三角形的三边的长分别是3、4、5，则这个三角形最长边上的高是         (    ) 

南半球缺失亚寒带针叶林带，其主要影响因素是（   ）

    How would you use a radio or a telephone if you had no electricity or batteries? This 1 bothered (使烦恼) British inventor Trevor Baylis. So in 1996, he 2 a wind-up (装有发条的) radio. It doesn't need any 3 or batteries. You wind it up by hand. It plays for about an hour. Then, you wind it up 4, and it plays for another hour. Today it's made in South Africa.

    Then in 1999, Baylis invented a mobile telephone that is powered by 5.The shoes have a small battery that is powered when you 6. This battery is connected to a mobile phone.

    These two simple inventions can bring 7 communications to all parts of the world. Baylis doesn't have a university degree in engineering. In 8, he left high school before graduating. He just loves 9 things to help people. He never knows when 10 will come to him. The idea for the telephone came to him in a dream.

2016年8月5日-22日，第三十一届夏季奥运会在巴西里约热内卢举行，来自200多个国家和地区约1．1万运动员参加了各个项目的角逐。读巴西轮廓图完成小题。