Observational studies are sometimes referred to as natural experiments. explain what this means

it should be c, women were allowed to vote in all states because federal law supersedes state law.

"states can make their own laws, as long as they don't contradict what the federal law states. the states do not have the authority to pass a law that negates a federal law." -google

answer; eliminate parking problems in cities, because a car took up only half as much space as a horse and buggy;