How Has Genetic Engineering Helped in the Treatment of Diabetes

How has genetic engineering helped in the treatment of diabetes in humans?

A) People have been engineered to have diabetes, and scientists have been able to test possible new treatments on them.
B) A vaccine has been developed by genetic engineering.
C) Pigs have been genetically engineered to produce human insulin, necessary for the treatment of diabetes.
D) Bacteria have been engineered to produce large quantities of human insulin, necessary for the treatment of diabetes, and scientists are close to being able to use this insulin in humans.
E) Bacteria have been engineered to produce large quantities of human insulin, necessary for the treatment of diabetes.