Question

Which of the following is an element?
(A) Aluminum
(B) Methane
(C) Hydrogen peroxide
(D) All of the above

Answer 1

Chemical elements are the purest form of atoms. Atoms combine to form molecules. Chemical compounds are a combination of chemical compounds. One of the examples of a chemical compound is methane with a chemical formula of $C{H_4}$ it is formed by the combination of two atoms.

Complete answer:
Atoms are tiny particles that consist of subatomic particles and are invisible to the human eye. Chemical elements are the purest form of atoms that consist of the same number of protons and electrons, which makes the element stable.
Chemical compounds are formed by a combination of chemical elements.
Aluminum is a chemical element with the chemical symbol of $Al$ , its atomic number is $13$ .
Methane is a chemical compound with a molecular formula of $C{H_4}$ , it was formed by the combination of one carbon atom and four hydrogen atoms. Thus, methane is a chemical compound.
Hydrogen peroxide is a chemical compound with a molecular formula of ${H_2}{O_2}$ , it is formed by the combination of two hydrogens and two oxygen atoms. Thus, hydrogen peroxide is a chemical compound.
Thus, aluminum is an element, and methane, hydrogen peroxide are compounds.
Thus, option A is the correct one.

Note:
Chemical elements do not break down into simple molecules by any chemical action. As aluminum is an element, it does not break down into simple substances. Chemical compounds can be broken down into simple substances by chemical action like hydrogen peroxide dissociates into radicals.