Answer: A
Explanation: Vaccines create memory cells with a weak version of the pathogen, so when they meet that pathogen again the body can respond more quickly and more efficiently since they have already been exposed to the pathogen.
Answer:
D
Explanation:
Photosynthesis by tiny marine plants (phytoplankton) in the sunlit surface waters turns the carbon into organic matter. Many organisms use carbon to make calcium carbonate, a building material of shells and skeletons
