Answer:
1) Stem cells can renew themselves by dividing into more stem cells more than once.
2) There are two types of stem cells: adult and embryonic stem cells.
3) Stem cells are not specific to one area in the body and can turn into skin, bone, blood or brain cells.
C is the answer. Particles erode from the main rock to form smaller rocks, and rock particles. It's the only answer that makes sense.
The relationship between the hermit crabs and the snails is A.commensalism
Why? Commensalism refers to a relationship where one organism benefits from the other without affecting it. In this case, the hermit crab benefits from the snails, via the latter's discarded shells. The crab's use of the snails' shells has no impact on the snails.