Correct Matches:
Element A) a substance that cannot be broken down into a simpler substance
Particle B) a tiny piece of matter
Scientific theory C) an explanation for some naturally occurring event
Atom D) the basic unit of an element
Explanation:
Every matter is made up of a number of atoms. Therefore, atoms are the basic unit present in a matter or element.
Element is defined as the substance that contains same type of atoms and it cannot be further divided into simpler substances.
A particle is defined as the smallest piece present in a matter.
Scientific theory is defined as the scientific explanation for a naturally occurring event.
Therefore, the given terms are matched with their definition as follows.
