Final answer:
The class of elements with properties of both metals and nonmetals in the periodic table is the Metalloids.
Step-by-step explanation:
The class of elements in the periodic table that has properties of both metals and nonmetals is known as metalloids (or semi-metals). These elements exhibit intermediate properties between metals and nonmetals and are typically found adjacent to the bold zigzag line in the right-hand portion of the periodic table. Examples of metalloids include boron, silicon, germanium, antimony, and tellurium. Among the options provided in the question (Alkali metals, Noble gases, Metalloids, Lanthanides), the correct answer is C) Metalloids.