In nuclear fission, atomic nuclei are
a. split
b. joined together
c. destroyed
d. created

Option (d) is the correct answer.

Explanation:

A reaction which causes a change in the rearrangement of atoms or chemical composition of a substance is known as a chemical change.

A chemical change can take place rapidly, slowly or too slowly.

For example, rusting of iron is a slow chemical change.

Therefore, the statement which is true about a chemical reaction is that it occurs whenever a chemical change takes place.