A substance made up of atoms of two or more different elements joined by chemical bonds.

• A. Compound
• B. Element
• C. Molecule
• D. Ion

Answer: (A)

A compound is a substance made from atoms of two or more different elements joined by chemical bonds. This matches the description because it requires different elements to be combined in a fixed ratio, giving the substance properties distinct from its constituent elements. An element is purely one type of atom, so it cannot be a compound. A molecule is any two or more atoms bonded together, and it can be just one element (like O2) or multiple elements (like H2O); the key is that a compound specifically involves at least two different elements. An ion is a charged particle formed by gaining or losing electrons and doesn’t define a substance by containing multiple elements.