Among the options provided, water has the highest heat capacity. Heat capacity is the amount of heat energy required to raise the temperature of a substance by one degree Celsius. Water’s high heat capacity means it can absorb and store a large amount of heat energy with only a small change in temperature. This property makes water exceptionally effective at regulating temperature, which is why it is widely used as a coolant in various applications and plays a crucial role in climate and weather patterns.

In contrast, substances like iron, gold, and benzene have much lower heat capacities, meaning they heat up and cool down more quickly when exposed to heat. Water’s superior heat capacity makes it unique and highly valuable for thermal management. Therefore, the correct answer is [B] Water.