For several billion years after the “Big Bang”, the earth was still just a cloud of dust. What it was to ______(36) was uncertain until between 4.5 and 3.8 billion years ago when the dust settled into a solid globe. The earth became so ______(37) that it was not clear whether the shape would last or not.
______(38) eastward, you’ll pass mountains and thousands of lakes and forests, as well as wide rivers and large cities. Some people have the idea ______(39) you can cross Canada in less than five days, but they forget the fact that Canada is 5500 kilometers from coast to coast. Here in Vancouver, you’re in Canada’s warmest part. People say it is Canada’s most beautiful city, _______(40 by mountains and the Pacific Ocean. Its population is increasing rapidly. The coast _______(41) of Vancouver has some of the oldest and most beautiful forests in the world.
However, this was not easy. When they first arrived in Gombe in 1960, it was unusual for a woman to live in the forest. _______(42) after her mother came to help her for the first few months ______(43) she allowed to begin her project. Her work changed the way people think about chimps. For example, one important thing she discovered was that chimps hunt and eat meat. Until then everyone ______(44) thought chimps ate only fruit and nuts. She also discovered how chimps communicate with each other, and her study of their body language helped her _____ _____(45) their social system.