Air : Atmosphere :: Water : ?

Answer: Option C

Analogy questions test your ability to see relationships between things. They ask you to find a pair of words that have the same relationship as another pair.

This question is asking: "If air is to atmosphere, then what is water to?"

Think about it this way: Air is the main component of the atmosphere. What is the main component of something else?

Let's look at the options:
Option A: Island - Islands are made of land, not water.
Option B: Earth - Earth is made of land and water.
Option C: Ocean - Ocean is a large body of water, just like the atmosphere is a large body of air.
Option D: Drop - A drop is a small amount of water.
Option E: Dew - Dew is water condensed on a surface.

Therefore, the best answer is Option C: Ocean because it shows the same relationship as air and atmosphere.