阅读短文，回答短文后的五个问题。

The world is full of amazing nature and discoveries. Here are two examples.

Rainbow mountains Danxia Landform

In Gansu, China, there is a row of mountains covered in coloured stripes. There are deep red, yellow, blue and green colours. They are more beautiful after the rain. These mountains look as if a rainbow has been painted over them. Some people have said, “These are the rocks where rainbows sleep.” These amazing rainbow mountains could be the imaginary landscape of an alien planet, but they are right here on Earth.

Titanosaur

For a human baby to grow to adult size takes many years. Not so, however, for a titanosaur baby. Titanosaurs are the largest dinosaurs that ever lived.

By studying the fossils (化石), scientists think that at birth titanosaur babies weigh as much as a human baby at birth. In just a few weeks, however, they were at least the size of a large dog. By around 20, they were bigger than buses. There are no other animals in the world that have started small and reached such a large size so ________. How amazing it is to think that something beginning as a tiny egg could grow into one of the largest animals ever to walk round the world!

注：每题答案不超过6个词。