ANS:D - all 'a', 'b' & 'c'

Certainly! Let's delve deeper into why each of the options presented is relevant to the occurrence of cavitation: a) Pressure falls below the vapor pressure: Cavitation occurs when the local pressure in a fluid drops below the vapor pressure of the liquid. When the pressure decreases sufficiently, the liquid turns into vapor or gas bubbles. These bubbles can collapse violently when they move to regions of higher pressure, causing damage to nearby surfaces. Thus, when the pressure falls below the vapor pressure, the likelihood of cavitation increases significantly. b) Pressure becomes very high: While cavitation typically occurs when pressure drops below the vapor pressure, extremely high pressures can also lead to cavitation. This situation can arise in certain scenarios such as the sudden collapse of vapor bubbles in a process known as inertial cavitation. In this case, the collapse of bubbles generates shock waves and high pressures, which can induce further cavitation events. Therefore, excessively high pressures can contribute to cavitation as well. c) Temperature becomes low: Temperature can also influence cavitation, albeit indirectly. Lower temperatures typically decrease the vapor pressure of a liquid. As a result, at lower temperatures, the pressure required to induce cavitation may be relatively lower. Additionally, colder temperatures can affect the fluid properties, viscosity, and other factors that influence cavitation behavior. Therefore, while temperature itself may not directly cause cavitation, it can play a role in influencing the conditions under which cavitation occurs. Considering all these factors, when pressure falls below the vapor pressure, pressure becomes very high, and temperature becomes low, the conditions are particularly conducive to cavitation. This comprehensive understanding helps us appreciate why all the options provided are relevant to the occurrence of cavitation.