Answer:
The answer is C.
Explanation:
We can use the process of elimination to get this answer.
A. Answer A. is incorrect because the essay is about a good friend of yours, not a friend who is good at singing. You could include this information about Betsy later on in the essay, but it is not a good introductory statement.
B. This is a good introductory statement, but it is more interpersonal than just a friend. It is pretty strong and could be used if this friend really helped change your life.
D. This is an impersonal statement. If Betsy Walton was one person among many others, that doesn't make her seem very special, like a good friend.