Horses and zebras can be bred to produce a zorse which is sterile which is most likely the reason zebras and horses are considered separate species

Your answer would be,  > The most likely reason zebras, and horses are considered separate species is: Their offspring cannot breed.

Hope that helps                                      : )

answer; the correct answer is desert plants;

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.