Answer:
The correct answer is B.
The scientists had a theory to explain the unusual relationships in their discovery.
Explanation:
Concrete nouns mean things that can be seen and touched. For example, "the Cat is lying on the grass", Cat is the Concrete noun, "the Gate prevents a lot from coming in". Other examples include, Spoon, Bag, Cloth, Car, Chair, book, etc.
Given the above, the appropriate answer is Scientists because it can be seen.
