A gateway substance is something that may be menial but could lead to something bigger, an example is weed in the drugs world, weed is not hard to get and is usually a gateway drug to stronger types of drugs and potentially more dangerous
Glucose and oxygen!!!
CO2 + Water in the presence of sunlight results in glucose + oxygen
Answer:
The immune system similar to a tiny police force that always patrols every organ and tissue inside the body. It works closely with the circulatory system for shipment needs and the lymphatic system for the production of lymphocytes.
Explanation:
I think the answer is either B or C, hope this helps! Sorry if it doesn't!