Answer:
The answer is d. vivid memories.
Step-by-step explanation:
The limbic system, among other things, is responsible for memory and emotions. Since smell is connected to this system, it is a very powerful sense memory-wise.
Another reason the sense of smell is so sensitive is because it has a long evolutive history. Most single-cell organisms rely on smell as a means of interaction, so naturally it has developed in humans and other mammals.