. . . . . . . . is a halogen. A. Sodium B. krypton C. magnesium D. chlorine

Sodium
krypton
magnesium
chlorine

The correct answer is D. Chlorine.

A halogen is a chemical element in the periodic table that is a member of Group 17. The halogens are reactive non-metals that form salts when they react with metals. They are also known as the “salt-formers”.

Sodium is a chemical element in the periodic table that is a member of Group 1. It is a soft, silvery-white metal that is highly reactive. It is the most abundant metal in the Earth’s crust.

Krypton is a chemical element in the periodic table that is a member of Group 18. It is a noble gas that is colorless, odorless, and tasteless. It is the third most abundant element in the Earth’s atmosphere.

Magnesium is a chemical element in the periodic table that is a member of Group 2. It is a silvery-white metal that is highly reactive. It is the eighth most abundant element in the Earth’s crust.

Chlorine is a chemical element in the periodic table that is a member of Group 17. It is a greenish-yellow gas that is highly reactive. It is the second most abundant element in the Earth’s atmosphere.