What two factors act together to keep earth in orbit around the sun

Gravity and inertia

Explanation:

Gravity is the force which keeps all the planets in its position. The sun has enough gravity to keep the planets in its orbit. Inertia is the force that makes sure that the planets continue to be in motion.Gravity and inertia work hand in hand so the planets are in their position and their speed is also maintained. If these two forces do not exist, then the earth's orbit would collapse.

Answer:   [a]:   "slate" .