Ans. (1) For preparing vaccines, in olden days,microbes were injected in the bodies of horses ormonkeys. These laboratory animals used to makeantibodies to defend these microbes. Antibodies areproteins which can act against the disease-causinggerms. These antibodies were extracted from theblood of these animals and were used as vaccines.(2) Now-a-days with the advent of biotechnology,the vaccines are manufactured in laboratories withthe help of bacteria. For this purpose, a detailedstudy of the disease causing germ is undertaken.The genes and the DNA of such microbes arethoroughly explored. Then based on thisinformation, proteins which can act against suchmicrobes are synthetically prepared in thelaboratories. The safe vaccine is produced in such away which can defend the body against infections.3) Some types of vaccines are prepared from theextracts of germs. These germs or microbes aredeactivated and made dormant. When they areinjected in the body of a person, they initiate thedefending action. The body of such vaccinatedperson, already develops the antibodies in his or herbody. When in future, this person is again attackedby similar germs the defence starts immediately andthe person does not become sick.
Red shirts and blue shirts equally count to his bonus, so he has 15 + 23 = 38 shirts sold at this moment. He needs to sell 75 shirts for the bonus. We subtract our goal from what he have; 75 - 38 = 37.
The strategy here: subtract the goal (75 shirts) from what you did to get to the goal (15 shirts and 23 shirts).
Nathan needs to sell 37 more shirts for the bonus. Hope this helps.
