No one knows how the huge rocks _______ and _______ without our modern machines eight hundred years ago.

Gaining the knowledge ________ environmental protection will help you to become a qualified environmentalist.

Wang Ping is one of the best students who _____from Beijing University. She studied politics, which _____the study of the ways in which a country is governed. [ ]

he help of high technology, in thepast few years, electronic business __________tobank industry, travel industry

We can communicate peoplein every part of the world theInternet．