In a system, static pressure of air increases with the speed of rotation of the fan. This is because when the speed of the fan is increased, the force with which it is pushing the air molecules is increased. Since pressure is a relationship between force and area, the pressure of the air molecules will be increased.
Conversely, when the speed of the fan is reduced, the priming force on the air molecules will be reduced, hence the pressure of the air will drop.
In the case of the fan, it requires an amount of pressure to blow air particles. The higher the pressure, the faster the rotation and the more the air particles will be blown .
This means the fan being turned from high to low speed indicates a reduction in the fluid pressure and amount of air particles blown. This validates option A.
Cetane rating of the diesel ensures the low temperature and uniform combustion. Centane number is just opposite to the octane number of petrol engine, cetane number of diesel determines at which temperature the diesel will going to autoignite.
