Answer:
A
Explanation:
A because water is a essential resource to humans and all types of life.
Answer:
B. White Blood Cells
Explanation:
I missed the word <em>innate</em> for a sec there, but then I looked up whether stomach acid is part of the immune system at all and realized my mistake.
The <em>innate immune system</em> is the part of the immune system one is born with, and we're not born with white blood cells. Those build up over time as we are exposed to pathogens.
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