Answer:
Orbital period, T = 1.00074 years
Explanation:
It is given that,
Orbital radius of a solar system planet, 
The orbital period of the planet can be calculated using third law of Kepler's. It is as follows :

M is the mass of the sun

T = 31559467.6761 s
T = 1.00074 years
So, a solar-system planet that has an orbital radius of 4 AU would have an orbital period of about 1.00074 years.
. In single particle problem whole mass is concentrated at a single point so it has a single displacement, single velocity and single acceleration. while, in rigid body mass is distributed
Answer:
B. The presence of an unbalanced force(e.g friction) causes a moving object to stop.
Explanation:
As the friction is that force that can stop the sled upon reaching the levelled surface so the option b is correct.
It is based on atomic number, which is the number of protons in the nuclei of the atoms of an element.