ANS:A - abundance & high heat capacity

Water is commonly used as a coolant in heat exchange equipment primarily because of its: Abundance and high heat capacity. Water is readily available in large quantities, making it a cost-effective choice for cooling applications. Additionally, water has a high specific heat capacity, which means it can absorb and carry away a significant amount of heat per unit mass without experiencing a large temperature increase. This property makes water an efficient coolant, allowing it to effectively transfer heat away from the system being cooled. While water does have a relatively low viscosity and high fluidity, these properties are not the primary reasons for its widespread use as a coolant. Similarly, its low density is not a significant factor in its selection as a coolant compared to its abundance and high heat capacity.