The analogy "Bark : Tree :: Scales : ?" is a part-to-whole analogy. In other words, it is comparing a part of something to the whole thing that it is a part of.
- Bark is a part of a tree.
- Scales are a part of a fish.
Therefore, the answer to the analogy is fish. This is because scales are a characteristic of fish, just as bark is a characteristic of trees.
The other options are incorrect because they are not parts of fish. Gills are used for breathing, elephants do not have scales, and dogs have fur.
Therefore, the correct answer is A.
Here is a table that summarizes the analogy:
| Part |
Whole |
| Bark |
Tree |
| Scales |
Fish |