1)(I)The car of the future looks something like this. (II)It has no engine,no steering column and no brake pedal.(III) It requires no gasoline,emits no pollution just a little water vapour and yet handles like a high performance Porsche ( IV ) The world must find a way to rid itself of its dependence on fossil fuels.(V)Instead of an internel combustion engine,for example,it is powered by fuel cells like those used in the orbiting space station.
2)(I)Farmers choose the crops they raise by considering the climate,the kind of soil and the condition of the market for agricultural products.(II) Planting different crops each year on a piece of land keeps the soil productive because one crop can benefit the next .(III) For example,nitrogen is essential for plant growth and is added to the soil by legumes,such as clover,alfalfa,soybeans and cowpeas.(IV) These combine nitrogen from the air with other elements and store it in the soil through their roots.(V) After the roots have rotted,other plants that need nitrogen but cannot use nitrogen in the air,like corn and potatoes,can use the stored nitrogen for growth.
3)(I )A simple test may be performed to determine whether a piece of rock is sandstone or limestone.(II)Limestone and marble are made up of the same chemicals.(III) Put a few drops of hydrochloric acid on the stone you are testing.(IV)If it is limestone,chemical action will take place ,and bubbles of gas will rise from the stone( V) No such bubbles will appear if the rock is sandstone.