Does a reservoir that has vapor(A) or solid water (B) have the longest residence time?

To answer this question, we first need to understand what residence time is. Residence time refers to the average time a particle spends in a particular system. In this case, we are comparing the residence time of water in two different states - vapor and solid - in a reservoir.

1. Vapor Water (A): The residence time of water vapor in a reservoir would depend on several factors such as temperature, pressure, and humidity. However, generally, water in its vapor state tends to have a shorter residence time. This is because water vapor is lighter and more mobile, and can easily be moved by wind and other atmospheric processes.

2. Solid Water (B): Solid water, or ice, tends to have a longer residence time in a reservoir. This is because ice is heavier and less mobile than water vapor. It is not easily moved by wind or other atmospheric processes. Additionally, the conversion of ice back into liquid water (melting) is often a slow process, especially in colder climates.

Therefore, a reservoir that has solid water (B) would generally have a longer residence time than a reservoir with vapor water (A).