Explanation
Correct answer: A.
Choice A is the best answer. "To that end" logically signals that the activity described in this sentence—Nazareth titling his course "Elvis as Anthology"—is meant to further Nazareth’s goal of helping others understand Presley’s music as an anthology with a wide range of influences.
Why the other choices are wrong
Choice B
Choice B is incorrect. "In sum" illogically signals that the activity described in this sentence summarizes Nazareth’s view of Presley’s music as an anthology. Instead, titling his course "Elvis as Anthology" is a way for him to promote this view.
Choice C
Choice C is incorrect. "That is" illogically signals that the activity described in this sentence is a clarification or interpretation of Nazareth’s view of Presley’s music as an anthology. Instead, titling his course "Elvis as Anthology" is a way for him to promote this view.
Choice D
Choice D is incorrect. "In addition" illogically signals that the activity described in this sentence is merely an additional fact about Nazareth. Instead, titling his course "Elvis as Anthology" is a way for him to promote his view of Presley’s music as an anthology.