Assertion `:` The focal length of the mirrorr is `f` and distance of the object from the focus is `u` , the magnification of the mirror is `f//u`.
Reason : Magnification `=("Size of the image")/("Size of object" )`
A. If both the assertion and reason are true and reason explains the assertion.
B. If both the assertion and reason are true but reason does not explain the assertion.
C. If assertion is true but reason is false.
D. If assertion is false but reason is true.