Answer:
Carbon reservoirs are underground oil or gas trap that form reees.clastic limestones etc.This is the most earths carbon stored in rocks and sediments.Ocean,Biosphere,Soil Carbon are some examples of carbon reservoirs.
Isotopes of an element are defined has that has same atomic number but different mass number mean they have different number of neutrons
so the statement that best describe a similarity is
<span> same atomic number; different mass number
</span>so correct option is C
hope it helps
