How many vitamins are known to be required in the diet of human beings? ?

Which statement describes both homogeneous mixtures and heterogeneous mixtures?

Transportation is the largest single source of air pollution in the united states. air pollution can harm the environment and human health. which technology could offer a solution to this problem? mufflers that reduce noise motors that run on electricity tires that improve gas mileage

If an area has high air pressure and low humidity, what type of weather will it most likely have? plz !