The correct answer is A. halogen.
Halogens are elements in the 17th group of the periodic table. They are highly reactive and form salts with metals. The three elements with atomic numbers 35, 53, and 85 are chlorine, iodine, and astatine, respectively. All three of these elements are halogens.
Alkaline metals are elements in the 1st group of the periodic table. They are highly reactive and form hydroxides with water. The three elements with atomic numbers 1, 3, and 11 are hydrogen, lithium, and sodium, respectively. None of these elements are halogens.
Inert gases are elements in the 18th group of the periodic table. They are highly unreactive and do not form compounds with other elements. The three elements with atomic numbers 2, 10, and 18 are helium, neon, and argon, respectively. None of these elements are halogens.
Halides are compounds that contain a halogen atom. The three elements with atomic numbers 35, 53, and 85 are chlorine, iodine, and astatine, respectively. All three of these elements can form halides with other elements. However, the term “halide” is more commonly used to refer to compounds that contain chlorine or bromine.