Magnification is the ratio of the image's height to object's height or the ratio of image distance to object distance.
That is; Magnification = height of the image/height of object= image distance/object distance
= x/4 = 21/8
x = (21 × 4)/8
= 10.5 cm
The height of the image is 10.5 cm
The mirror in this case is a concave mirror, since when the object is placed between the principal focus and the concave mirror, it forms a virtual magnified image on the other side ofthe mirror (that is why we have a negative image distance).
Galileo, in full Galileo Galilei, (born February 15, 1564, Pisa [Italy]—died January 8, 1642, Arcetri, near Florence), Italian natural philosopher, astronomer, and mathematician who made fundamental contributions to the sciences of motion, astronomy, and strength of materials and to the development of the scientific method. His formulation of (circular) inertia, the law of falling bodies, and parabolic trajectories marked the beginning of a fundamental change in the study of motion. His insistence that the book of nature was written in the language of mathematics changed natural philosophy from a verbal, qualitative account to a mathematical one in which experimentation became a recognized method for discovering the facts of nature. Finally, his discoveries with the telescope revolutionized astronomy and paved the way for the acceptance of the Copernican heliocentric system, but his advocacy of that system eventually resulted in an Inquisition process against him.
Options A and C are correct but if you compare their masses, person has negligible mass compared to car. So a car at the top of the hill has the most potential energy.