Why Can a Person Who Is Unable to Produce Insulin

Why can a person who is unable to produce insulin be successfully treated with insulin derived from genetically modified bacteria?

A) Typical bacterial insulin is exactly the same as human insulin.
B) The gene that produces insulin in humans was inserted into the bacteria where it continues to produce human insulin.
C) The insulin-producing gene of bacteria was altered to have the same base sequence as the human counterpart and now produces the human version of insulin.
D) Bacterial insulin is similar enough to human insulin to serve the same purpose.