Question

Which of the following arguments correctly justifies the second step of the flow proof of the triangle angle sum theorem below

Answer 1

We need to see the second step of the proof, so we know what needs to be justified. It would also be nice to see the list of answer choices. I'll never understand how someone who can't answer the question and has to ask someone else can then go ahead and decide that the person helping him only needs to see parts of the question.