What kind of motion will an object have when forces on it are balanced? It will not move at all.
It will move very fast.
It will start moving slowly, then speed up.
It will move only slightly.

heat a spark and oxygen

they deliver oxygen to the blood

c is the correct answer hope this !

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.