The correct answer is D. Sulphur.
Sulphur is a non-metal that is not alkaline. It is a pale yellow solid that is found in nature as the mineral sulfur. Sulphur is an important element in many compounds, including sulfuric acid, sulfur dioxide, and hydrogen sulfide.
Sodium, potassium, and lithium are all alkali metals. Alkali metals are highly reactive metals that are found in Group 1 of the periodic table. They are all soft, silvery-white metals that react violently with water to form alkaline solutions.
Alkaline solutions are solutions that have a pH greater than 7. They are basic solutions that can neutralize acids. Alkaline solutions are often used in cleaning products and in the treatment of acid reflux.