What do astronomers refer to as the retrograde motion of the planets

Astronomers use the term to refer to the occasional backwards motion of the planets as seen in Earth's sky. When used in this way, retrograde motion is entirely an illusion caused by the moving Earth passing the outer planets in their orbits.

retrograde motion

Explanation:

Astronomers use the term to refer to the occasional backwards motion of the planets as seen in Earth's sky. When used in this way, retrograde motion is entirely an illusion caused by the moving Earth passing the outer planets in their orbits.

they start with the same

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.