Which of the following conditions causes air binding?

Air binding typically occurs when there is a decrease in pressure accompanied by an increase in temperature. This combination can lead to a situation where dissolved air in water systems can come out of solution and form bubbles, effectively binding with and obstructing the flow of water.

Under normal conditions, water can hold a certain amount of dissolved gases, including air. However, if pressure drops, it reduces the water's ability to hold that air, and if the temperature increases, the solubility of the gas decreases even further. This scenario can particularly happen in water transmission or distribution systems where there might be points of lower pressure due to elevation changes or pipe restrictions, and if temperatures are additionally high, the risk of air binding increases.

In contrast, the other options either involve conditions that do not lead to significant air release or scenarios where the physical parameters actually promote the solution of gases in the water rather than causing air binding. Understanding the interplay of temperature and pressure is key when managing water systems to prevent issues such as air binding, ensuring efficient flow and operational stability.