The correct answer is: A. Its ignition temperature is very high.
Phosphorus is a highly reactive element that can ignite spontaneously in air at temperatures as low as 40 degrees Celsius. It is therefore stored in water to prevent it from igniting. Water acts as a coolant and prevents the phosphorus from reaching its ignition temperature.
The ignition temperature of a substance is the minimum temperature at which it will ignite and start burning. The ignition temperature of phosphorus is very low, which means that it can ignite easily. This is why it is important to store phosphorus in water to prevent it from igniting.
The critical temperature of a substance is the temperature above which it cannot exist as a liquid. The critical temperature of phosphorus is 482.3 degrees Celsius. This means that phosphorus cannot exist as a liquid above this temperature.
The critical temperature of a substance is not related to its ignition temperature. The ignition temperature is the minimum temperature at which a substance will ignite and start burning, while the critical temperature is the temperature above which a substance cannot exist as a liquid.