The correct answer is D. Yttrium.
Isotopes are atoms of the same element that have different numbers of neutrons in their nucleus. Hydrogen has three naturally occurring isotopes: protium, deuterium, and tritium. Protium has one proton and no neutrons, deuterium has one proton and one neutron, and tritium has one proton and two neutrons. Yttrium is an element with the atomic number 39. It has no isotopes with the same number of protons as hydrogen.
Protium is the most common isotope of hydrogen, making up about 99.98% of all hydrogen atoms. Deuterium is less common, making up about 0.02% of all hydrogen atoms. Tritium is the least common isotope of hydrogen, making up only about 10-18% of all hydrogen atoms.
Isotopes can have different chemical properties than each other. For example, protium is the only stable isotope of hydrogen. Deuterium and tritium are both radioactive, meaning that they decay into other elements over time.
Isotopes can be used in a variety of applications, including nuclear power, medical imaging, and research.