The answer is C. Iodine.
Hydrogen, oxygen, nitrogen, and chlorine are all elements in the same group of the periodic table, the halogens. Halogens are highly reactive elements that form salts with metals. Iodine is the only non-metal in this group.
Hydrogen is the lightest element in the universe. It is a colorless, odorless, and tasteless gas that is essential for life. Oxygen is a colorless, odorless, and tasteless gas that is essential for respiration. Nitrogen is a colorless, odorless, and tasteless gas that makes up about 78% of the Earth’s atmosphere. Chlorine is a greenish-yellow gas that is used in bleach and disinfectants.
Iodine is a non-metallic element that is solid at room temperature. It is a dark purple-black solid that is used in antiseptics and dyes.