These preparations are called Vaccines. <span>A </span>vaccine<span> is a biological preparation that
provides active acquired immunity to a particular disease. A </span>vaccine<span> typically contains an agent that
resembles a disease-causing micro-organism and is often made from weakened or
killed forms of the microbe, its toxins or one of its surface proteins</span>. I
am hoping that this answer has satisfied your query and it will be able to help
you in your endeavor, and if you would like, feel free to ask another question.
Answer:
b. testing new conditions.......
I think it is the 3rd one because health problems at older age.
It is said that the materials found in the giant cloud that formed our solar system are comparable to the ones we have in the solar system today, which are Hydrogen and Helium!
