Concept:Substitute n=3 and n=4 into the given nth-term formula, then add the results.Explanation:The nth term is n2−6n−4.For the 3rd term, set n=3:32−6(3)−4=9−18−4=−13.For the 4th term, set n=4:42−6(4)−4=16−24−4=−12.Sum of the 3rd and 4th terms:−13+(−12)=−25.Answer:−25 (Option D).