Answer:True
Explanation:Viruses are a very huge problem these days as they are a 100 times bigger than an actual blood cell or bacteria a virus is just a bunch of bacteria in one big bunch
It is intended to increase immunity against that antigen back to protective levels, after memory against that antigen has declined through time.
Answer:
Option D, all of the above
Explanation:
Industrial revolution caused creation of wealth and generation of income due to which people living in remote/village areas migrated towards cities in large number which led to population explosion.
With the advent of new machines and tools (such as guns, strong fishing nets, distinctive sharp tools etc.), the hunters (such as poachers, fishermen , slaughter house workers etc.) got enabled and hence their number also increased.
New methodologies of trash disposal were also created such as incineration.
Hence, option D is correct