The correct answer is B. Inert gases.
The elements of group 18 are the noble gases, also known as inert gases. They are all non-metals and have very low chemical reactivity. They are all monatomic gases at standard temperature and pressure. The noble gases are helium, neon, argon, krypton, xenon, and radon.
Alkali metals are the elements in group 1 of the periodic table. They are all highly reactive metals that are soft and have a low melting point. The alkali metals are lithium, sodium, potassium, rubidium, cesium, and francium.
Halogens are the elements in group 17 of the periodic table. They are all highly reactive non-metals that are diatomic gases at standard temperature and pressure. The halogens are fluorine, chlorine, bromine, iodine, and astatine.
Alkaline earth metals are the elements in group 2 of the periodic table. They are all highly reactive metals that are harder than the alkali metals and have a higher melting point. The alkaline earth metals are beryllium, magnesium, calcium, strontium, barium, and radium.