Compounds have: 

Chemical compounds can be described as any substance with two or more different types of atoms (chemical elements) arranged in a definite stoichiometric ratio; the concept is best understood when applied to pure chemical substances. Chemical compounds are held together in a distinct three-dimensional arrangement by chemical bonds and have a distinct and defined chemical configuration.

In the case of compounds, the molecules must contain more than one sort of element. As a result, molecules with just one sort of element cannot be referred to as compounds. For example molecular oxygen $\left({\mathrm{O}}_2\right)$.
As a compound changes, the number of unique atoms it contains may alter. The number of atoms that are present in a particular compound molecule are indicated by the chemical formula, such as, in water, since hydrogen and oxygen are two separate elements, we can say that ${\mathrm{H}}_2\mathrm{O}$ is a compound.
As a result, we can say that compounds are made up of atoms from several elements combined in a specific ratio.
Chemical compounds can be salts that are bound together by ionic bonds, intermetallic compounds that are bound together by metallic bonds, molecular compounds that are bound together by covalent bond, or the subset of chemical complexes that are bound together by coordinate covalent bonds.

Hence, the correct answer is option A.