Answer: D. The number of protons in the nucleus changes.
Explanation:
Transmutation occurs due to a change in the number of protons in the nucleus as this will cause the element to either become another isotope of the same element or an entirely new element altogether.
There are two types of transmutation; Natural and Artificial. Natural transmutation happens as unstable elements such as Uranium-238 try to find stability. They decay until they become a stable element. Artificial transmutation happens when atoms are collided with particles that cause them to change.
