Which is responsible for muscle pain felt after repeatedly lifting weights

I found out what causes muscle soreness after workouts. Since the early 20th century, this specific type of muscle soreness, called “delayed onset muscle soreness” (DOMS), was thought to be cause by lactic acid buildup in the muscles during strenuous workouts where your body's oxygen supply is depleted.

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.