Vaccines have been subjected to quite a bit of controversy in recent years. currently, the centers for disease control and prevention (cdc) recommend that healthy people receive a flu vaccine every year.
what are your current perceptions of the flu vaccine? do you think these recommendations are appropriate? explain your reasoning.

well, i believe that the answer is 2. : 3

they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.