Who is known as the 'Father of Modern Astronomy'?

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A : An electric fan continues to rotate for some time after the current is switched off.

Reason R: Fan continues to rotate due to inertia of motion.

In the light of above statements, choose the most appropriate answer from the options given below.

If $M$ is the mass of the earth and $R$ its radius, the ratio of the gravitational acceleration and the gravitational constant is

Suppose the gravitational force varies inversely as the ${\mathrm{n}}^{\mathrm{t}\mathrm{h}}$ power of distance. Then the time period of a planet in circular orbit of radius $\mathrm{R}$ around the sun will be proportional to -

Suppose the gravitational force varies inversely as the $n^{th}$ power of the distance. Then the time period of a planet in circular orbit of radius $R$ around the sun will be proportional to