What Is Incorrect About Mixing Insulin

What is incorrect about mixing insulin?

A) Roll regular insulin to mix before drawing up the amount needed.
B) When mixing two insulins, draw up the regular insulin first.
C) Rotate injection sites to prevent tissue damage.
D) Air needs to be added to both vials before any insulin is drawn up.
E) If air bubbles are in the syringe with the two insulins, the syringe must be discarded, and the insulin needs to be redrawn up.