What’s the answer to the question

Which statement best describes how atoms combine to form sodium chloride (nacl)? a. a positively charged sodium ion and a positively charged chlorine ion form an covalent bond. b. a positively charged sodium ion and a negatively charged chlorine ion form an covalent bond. c. a positively charged sodium ion and a positively charged chlorine ion form an ionic bond. d. a positively charged sodium ion and a negatively charged chlorine ion form an ionic bond.

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

Witch two conditions can limit the usefulness of the kinetic molecular theory in describing gas behavior?