The change that is undergone by an atom of an element made radioactive by bombardment with high-energy protons is called(1) natural transmutation(2) artificial transmutation(3) natural decay(4) radioactive decay

The correct answer is Option 2.

Explanation:

Natural transmutation is defined as the decay process of the radioactive elements which occur spontaneously by a process that causes transmutation.

Artificial transmutation is defined as the process where artificially induced nuclear reaction is done by the bombardment of nucleus with high energy particles on a radioactive element. It is a spontaneous reaction.

Natural decay or radioactive decay are the processes in which a nucleus disintegrates spontaneously on its own. There are many processes by which this decay takes place.

Hence, the correct answer is Option 2.