What is a deuteron composed of?

The deuteron is indeed composed of one proton and one neutron. In nuclear physics, a deuteron is the nucleus of deuterium, which is an isotope of hydrogen. This isotope helps to distinguish itself from the more common form of hydrogen, which contains only one proton. The presence of an additional neutron in the deuteron allows for unique properties, such as its stability and its role in nuclear reactions, particularly in fusion processes. Understanding the composition of the deuteron is essential for studying topics such as nuclear physics, chemistry, and various applications in medical imaging and radiation therapies.

The other options represent incorrect combinations of protons and neutrons that do not fit the definition of a deuteron: two protons and two neutrons describe helium-4, one proton and two neutrons does not correspond to any stable or commonly known isotope, and one neutron and one electron cannot exist as a nucleus (as electrons are not part of the nucleus).