Answer:
Ca and B
Explanation:
By definition, an element is the most basic substance that can't be simplified. Molecules are when two or more atoms of the same type of element join together. Compound is when two or more different elements join together. Following these definition, Ca (Calcium) and B (Boron) are elements. O₂ is a diatomic molecule while KF (Potassium Fluoride) is a compound.
