Why Can a Person Who Is Unable to Produce Insulin,be

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) Human insulin was inserted into bacteria and when the bacteria reproduce,so too does the insulin.