The answer is D........................
A.) A car door since it lets people come in and get out. But, only who allows to come in. Ex: Like the members of the cells or the people entering/exiting the car.
Answer:
They are secreted from pancreatic cell through exocytosis.
Explanation:
Beta cells of the pancreas are responsible for the synthesis and release of insulin in the blood. Insulin is released in the blood when the blood glucose level reaches above the normal blood glucose level.
Once the beta cells are insulated the insulin is released from the cell by the process of exocytosis and reaches to blood capillaries of islets. Insulin is made up of A and B chain when released in the blood but in proinsulin, a C chain is also present which is released in mature insulin.
Therefore exocytosis is responsible for releasing insulin from the Beta-cell of the pancreas.
Evolution of new diseases I think is the answer you're looking for.