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.