Explanation:
The odd one out in this list is option A - Valley : Depth.

Valley : Depth
- A valley refers to a low area of land between hills or mountains, often with a river flowing through it.
- Depth, on the other hand, refers to the measurement of how deep something is, such as the depth of a lake or the depth of the ocean.

The key difference between the words in this pair is that "valley" refers to a specific geographical feature, while "depth" is a more general term used to describe the measurement of how deep something is.

High : Low
- High and low are antonyms and opposite in meaning.
- High refers to an elevated position or a measurement above the average or normal level.
- Low, on the other hand, refers to a position or measurement below the average or normal level.

Good : Bad
- Good and bad are antonyms and opposite in meaning.
- Good refers to something that is morally right, virtuous, or beneficial.
- Bad, on the other hand, refers to something that is morally wrong, harmful, or of poor quality.

Black : White
- Black and white are antonyms and opposite in color.
- Black is the absence or complete absorption of light, resulting in a dark color.
- White, on the other hand, is the presence of all colors of light combined, resulting in a bright color.

Conclusion:
The odd one out in this list is option A - Valley : Depth. The other pairs consist of antonyms or opposites in meaning, while the pair "valley" and "depth" are not directly opposite in meaning and have different levels of specificity.