___used to be thought that the earth was square.
. It is the test system, _____ the teachers, that is to blame for the heavy burden of middle school students nowadays.
. To the surprise of many people, in ten years the city’s population ____ by 12%.
--What about the protection? ---Let’s keep the surface ____ dirty by putting a cover over it.
. The order _____the general gave was _____we must break through the enemy’s defence .
.The most ____news was that my parents were so ____with my school grades.