Pls help! Will mark brainliest!

To be considered they must have lived over a very short period of time and had to be many of them.

A) An index fossil
B) A trace fossil
C) A petrified fossil
D) A carbon fossil

A) Index Fossils

Explanation:

Index fossils are fossils used to define and identify geologic periods. Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends.

d: the voltage of the secondary coil is less than that of the primary coil.

im not suree sorry if wrong

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.