Gravity is a force that is important in understanding planetary science. Select the statements that are TRUE.
There is no gravity on the Moon.
Gravity played a key role in the formation of the solar system.
There is virtually no gravity in space.
Gravity causes objects dropped on Earth's surface to fall toward the Earth.
If a planet has no atmosphere it has no gravity.
Gravity keeps planets in orbit around the Sun and the moon ins orbit around planets.

the first phase of the government’s plan for settlement was building the transcontinental railroad. the railroad provided a way to bring settlers and manufactured goods west and ship their agricultural and mining produce east. the transcontinental railroad was an essential artery for rapid development of the frontier.

the second phase of the government’s plan was a liberal land distribution policy that made it possible for many people to homestead. with these two key elements—transportation and cheap land—the government rapidly achieved its goal of persuading people to move west, settle on farms, and push back the frontier.