How long does water vapor remain in air

That depends on the temperature of the area! If you can provide further information, perhaps I or someone could help you more specifically.

The hotter it is, the more likely the water is to stay in the air. The colder it is, the more likely the water is to condense!

Reservoir time is highly variable, depending on the type of reservoir. For example, water stays in the atmosphere for only nine days on average. By contrast, once water reaches the ocean, it stays put for a very long time - an average of more than 3,000 years.

The correct answer is d