The period of a planet around the sun is $8$ times that of earth. The ratio of the radius of the planet's orbit to the radius of the earth's orbit is:

$A$ planet revolves around the Sun in an elliptical orbit,where the semi-major axis $a$ is double the semi-minor axis $b$ $(a = 2b)$. The Sun is at the focus. Given that the planet takes $24$ hours to travel through the path $bed$ as shown in the figure,find the time taken by the planet to travel along the path $dab$.

The distance of a planet from the sun is $5$ times the distance between the earth and the sun. The time period of the planet is

Two planets move around the sun. The periodic times and the mean radii of the orbits are $T_1, T_2$ and $r_1, r_2$ respectively. The ratio $T_1/T_2$ is equal to

$A$ planet orbits the sun in an elliptical path as shown in the figure. Let $v_P$ and $v_A$ be the speed of the planet when at perihelion and aphelion respectively. Which of the following relations is correct?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ The radius vector from the Sun to a planet sweeps out equal areas in equal intervals of time and thus the areal velocity of the planet is constant.
Reason $(R):$ For a central force field,the angular momentum is a constant.
In the light of the above statements,choose the most appropriate answer from the options given below: