Which is true of planetary orbit a. they travel in elliptical orbits with the sun in the center b. the speed is the greatest when the plancts are closest to the sun in their orbits. c. the outer planets travel faster, but because of their huge orbits, they still take to go around the sun than the inner planets travel around the celestial sphere in a single direction, appearing to stop and back up phases just like the moon does as seen from earth. e. all the planets go through

B is true

Explanation:

This question seems to be incomplete or wrongly written, anyway B is the only one that is true.

Planetary orbits have kinetic and potential energy, the sum of these remains about constant. When closest to the Sun the planet has the lowest potential energy, at this point kinetic energy is maximum, and since speed is related to kinetic energy

at maximum kinetic energy speed is maximum too.

A is false because while planets do travel in elliptical orbits, the Sun is not at the center but in one of the focuses.

C is false, you can check the orbital speeds of any of the outer planets. They are slower because at the heigt the orbit there is a smaller gravitational pull. SInce the gravitational pull is the centripetal force, and orbital speed depends on this force, their speed is slower.

this is poiselle's equation from fluid mechanic in physics. mech eng