Ammonite is a species of shellfish that is used as an index fossil. it has a distinct spiral shell. which statement most likely explains why other species of shellfish that existed around the same period of time are not considered index fossils?
a.
other shellfish did not contain the carbon-14 isotope.
b.
other shellfish were much smaller in size than ammonites.
c.
other shellfish were not as widespread as ammonites.
d.
other shellfish did not have a rigid external body, like ammonites. match each process to where it occurs in the carbon cycle.

The answer is C. Other shellfish were not as widespread as ammonites.

Explanation:

Ammonites is a group of marine animals that no longer exist due to extinction. They are classified to phylum Mollusca. Ammonites are identified by their external coiled shells that are preserved as fossils. They are used as Index fossils because the rocks having ammonites fossils can be linked to a specific geologic time zone. Ammonites were present in abundance and had wide geographical distribution making them excellent candidate of index fossils.

answer; i believe is(b)converging

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.