3.Greenland._____is land in the world,covers over two million square kilometres.

D "the largest island in the world"修饰 GREENLAND的,具体的谓语在逗号后面,即 cover

greenland, the largest island in the world, covers two million square kilometres
格陵兰，世界上最大的岛屿，占地两百万平方公里。