Classification is subject to change because science is an evolving subject. New things are discovered every year and thus changing the way we understand the world around us.
Answer:
The hardness rating is 4.
Explanation:
Calcite sits at a hardness rating of 3 and is very easily scratched with a knife and/copper coin. This is where most Marbles, limestones, travertines, rate.
Meanwhile, Fluorite sits at hardness 4 and can be scratched by a knife.
External skeleton is the correct answer. Hope this helps out !
After meiosis you are left with 23
