Which statement is true? a molecule having a covalent bond can be ionic. a molecule having a covalent bond is always polar. a molecule having a covalent bond may be polar or nonpolar. a molecule having a covalent bond is always nonpolar.

A molecule having a covalent bond may be polar or nonpolar.

Explanation: Covalent bond is formed by sharing of electrons and ionic bond is formed by transfer of electrons.

Thus ionic molecules are always polar as they are formed by combination of positively charged ions called cations formed by less electronegative metals and negatively charged ions called anions formed by more electronegative nonmetals.

Covalent molecules which are formed by same elements have no difference in electronegativities are non polar but those formed by different elements having difference in electronegativities are polar.

For eg: Covalent molecule is non polar but covalent molecule is polar.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)