如图8-2-9所示，F1等于F2，下列各对力中不属于二力平衡的是（　　）

在一个光滑的水平面上，用绳子拉小车做直线运动，当小车的速度达到4m/s时，绳子脱落，这时小车在水平面上做　 　运动，小车的运动速度是　 　．

解：分析题意可知，当拉小车的绳子突然断开时，小车由于惯性仍要保持原来的运动状态不变，即小车在水平面上做匀速直线运动，其速度仍为4m/s．

故答案为：匀速直线；4m/s．

“Food Safety”has become one of 　 　topics recently.

A.hot B.hotter C.hottest D.the hottest

The news caused great 　 　 (excite) among her friends.

答案：excitement

Humans catch 　 　 for meat, fat and oil.

A. whales B. dolphins C. octopuses D. pandas

Tigers and lions are 　 　 animals.

答案：wild

An 　 　 panda weighs many times more than a baby panda.

答案：adult

The Chinese 　 　 is going to plant more bamboo trees for the pandas.

答案：tourists

The old woman died from 　 　 (ill) at last.

答案：illness

Flying across the Atlantic for the first time was a great 　 　 (achieve).

答案：achievement