The correct answer is the third one
Answer:
Helper T-cells stimulate B-cells to make antibodies and help killer cells develop. Killer T-cells directly kill cells that have already been infected by a foreign invader. T-cells also use cytokines as messenger molecules to send chemical instructions to the rest of the immune system to ramp up its response.
Answer:
The circulatory system is made up of blood vessels that carry blood away from and towards the heart. Arteries carry blood away from the heart and veins carry blood back to the heart. The circulatory system carries oxygen, nutrients, and hormones to cells, and removes waste products, like carbon dioxide.
Your circulatory system delivers oxygen-rich blood to your bones. Meanwhile, your bones are busy making new blood cells. Working together, these systems maintain internal stability and balance, otherwise known as homeostasis
Explanation:
Answer: A
Explanation: A heart attack (myocardial infarction) happens when one or more areas of the heart muscle don't get enough oxygen. This happens when blood flow to the heart muscle is blocked.
