Of the six-billion-plus people in the world,600 million live on islands.In other words,one in ten of the world's population is an island dweller.This is not so hard to imagine when you consider that more than 200 million people live in Indonesia alone--and about 60 million more live on the island of Britain. No island,or group of islands,is the same.Indonesia,for example,is a nation which consists entirely of islands,nearly 14,000 of them,of which 6,000 are inhabited.Britain is a small, crowded island,with a population density of 243 people per square kilometer,almost twice as much as China.Britain is also the only island in the world which is connected to a continent by a tunnel,the Channel Tunnel between southeast England and North France. If you ignore Australia,which is an island-continent,the largest island in the world is Greenland,an unusual name for a place which is almost permanently covered in ice! On the other hand,Iceland,which is Greenland's  ly near neighbor to the east,is much greener. Why is this?Iceland is far enough north,like Greenland,to be entirely covered by ice,but more than one third of Iceland is volcanically active.Magma,which is molten volcanic rock below the surface of the ground,heats the terrain above it,keeping it green.The story goes that an early settler from Iceland gave Greenland its name in order to encourage more people to live there! Even the smallest islands have a story to tell.The remotest inhabited island in the world is Tristan da Cunha,which is in the South Atlantic Ocean.Fewer than 250 people live there and they are all related to each other,with only seven surnames between them.The island capital has the romantic name of Edinburgh of the South Seas. According to the text,islands contain  _  .
one in ten of the world's population more than six billion people a total of 200,000,000 people much less than 10 percent of the world's population