Answer:
Explanation:The four closest to the sun — Mercury, Venus, Earth and Mars — are the terrestrial planets. They have rocky surfaces enclosed by relatively shallow atmospheres.
A hypothesis is an educated prediction that can be tested.
When the velocity of an object changes, it is acted upon by a force
Answer:
Only main sequence stars have a well-defined relationship between spectral type and luminosity.
Explanation:
Low-mass stars have much longer lifetimes than high-mass stars.
