Interpersonal conflict can result in
a. the deepening of a relationship
b. the end of a relationship
c. both a and b
d. none of the above

Personall I think that an interpersonal conflict can result both in the deepening of a relationship and in  the end of a relationship, but I think that the more typical answer is "b" and you should choose "b".

The reason why I think that an interpersonal conflict can result in the deepening of a relationship is that if the conflict is solved in a respectful way, the two people will know that they will continue being friends even if they disagree on some issues, which will deepen their friendship.

It's most likely choice a, it makes the most sense in my opinion.