A. He should add shells that are different colors, but the same size and type, to the tank and observe which shells the hermit crabs choose.
Durning an experiment you need to keep everything the same but only change the certain things based on your theory.
Such as how the student wanted to see if the color attracted the crab. If he had changed the size and type of the shell then the crab would have chosen the bigger one as they tend to grow into larger shells.
Answer:
non-specific system
Explanation:
The non-specific immune system is the system that works 24 hours a day, 7 days a week and protects you, regardless of the organism you encounter. This system is composed of the general defenses of the organism that work continuously, creating barriers that protect the body from the entry of any pathogen or foreign substance. This system is composed of T cells, which are true killers of pathogens and which guarantee efficient and complete safety.
Answer: Minerals
Hope this helps!
