How does atom electronegativity affect bond character and molecular polarity?

In case of heteroatomic molecules there is possibility of difference in electro negativity of the two hetero atoms bonded, this results in development of charges on the two atoms

more electronegative element will have a negative charge

less electronegative element will have a positive charge

Case

a) if the difference is less than 0.4 the molecule is  nonpolar.

b) if the difference is from 0.4 to 1.7 the molecule is  polar covalent.

c) if the difference is more than than 1.7 the molecule ionic (polar).

answer; i believe that the correct answer is (a); a large rock being weathered by wind and rain;

a chemical reaction happens

explanation: