How can internal combustion engines be modified to make auto exhaust free from pollutants ?

For an internal combustion engine to move a vehicle down the road,it must convert the energy stored in the fuel into mechanical energy to drive the wheels. In your car,the distributor and battery provide this starting energy by creating an electrical "spark",which helps in combustion of fuels like gasoline. Below is the reaction depicting complete combustion of gasoline in full supply of air: 2C_8 H_(18)(l) +25 O_(2) (g) to 16 'x' ‘A student while walking on the road observed that a cloud of black smoke belched out from the exhaust stack of moving trucks on the road.’ Choose the correct reason for the production of black smoke:

How can water pollution be controlled?

Pasteurization makes foodstuffs free from:

Explain how air pollution can be minimised.

In internal combustion petrol/diesel engines, only cyclic processes are used, because:

What is thorn? How can you tell it is modified stem?