The most remarkable weapon invented by primitive man is the boomerang. It is still used by the natives of Australia. Made of hard wood, it is shaped into a curve over hot coals. It is from two to four feet long, flat on one side and rounded on the other, with a sharp edge. There are several kinds of boomerangs. They are used for war, for hunting, and for amusement. The well-known "return" boomerang is really a toy. Instead of going straight forward, it slowly rises in the air. It whirls around in a curved line until it reaches a certain height, after which it returns to the thrower. This effect is produced by the action of the air on the bulging side of the boomerang. The other types are effective weapons because of their size and irregular motion. It is said that with one of these weapons, a native can cut a small animal almost in two at a distance of 400 feet.

Q. Underline the sentence which suggests that the natives of Australia use boomerangs expertly.