# Orbital period of planets

Level 1

The above graph shows the relationship between the orbital period (T) and the semi major axis (a) of the eight planets of the sun. Which of the following explanations is correct?

a) The orbital period is proportional to the semi major axis.

b) The orbital period is inversely proportional to the semi major axis.

c) The square of the orbital period is proportional to the semi major axis.

d) The square of the orbital period is proportional to the cube of the semi major axis.

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