The amount of carbon in fossils and artifacts decreases when the get older, so you can find out how old an object or fossil is by finding out how much carbon is in it.
Answer:
Covalent Bond
Explanation:
In the diagram Carbon and each of the 4 Hydrogens are sharing electrons. They are also both non metals. Both of these are characteristics of Covalent Bonds.
Cutting of Nails is a Physical Change since no new substance is formed.
Don't confuse it with Reversible and Irreversible Changes