Let pbe the set of polynomials. let a, b, c and d be elements of psuch that band dare non-zero elements of p which of the following is true
regarding the sum below?
a.
the sum is a rational expression
b.
the sum is a rational number
c.
the sum is a polynomial.
d.
the sum is an integer.

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.