List three things that scientists about earth beginning in the 1800s

What do you think was a drawback to this method of calculating distance

How voting rights have changed since the end of the civil war

How are the republican and democratic presidential candidates chosen? a. they are nominated by their state governments. b. each is nominated by his or her respective party. c. each is chosen by the governor of his or her home state. d. they are chosen by the house of representatives.