What effect does oxygen have on kelp

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.

yes. we have only a limited amount of land and space, and every plant is adapted to its own environment. through gene manipulation, we could perhaps create plants that can grow in a wide variety of environments, grow taller or wider, or be more resistant to diseases.

(this is the exact answer provided by the system)