求一些短小的英文科技文

1)
Helicopters are very convenient for dropping freight by parachute,but this system has its problems.Somehow the landing impact has to be cushioned to give a foft landing.The movement to be absorbed depends on the weight and the speed systems bounce the load as it lands,sometimes turning it over.To avoid this,Bertin,developer of aerotrain,has come up with an air-cushion system which assures a safe and soft landing.

2)
Everyone agrees that water pollution is a serious problem today.Oceans,lakes,and rivers all over the word are becoming polluted with garbage and dangerous chemicals,Factories contribute to the problem because they rely on the rivers for disposing of wastes.Oil and other chemicals can kill fish and people make water bad for drinking.Polluted water is hazard to everyone.Since people are dependent on water,they should be involved in finding a solution to this problem.

3)
The threat of impending financial disaster concentrates polit