Which biconditional statement is true?
a. a shape is a rectangle if and only if the shape has exactly four sides and four right angles.
b. a shape is a trapezoid if and only if the shape has a pair of parallel sides.
c. a shape is a triangle if and only if the shape has three sides and three acute angles.
d. a shape is a square if and only if the shape has exactly four congruent side

Answer;

A .a shape is a rectangle if and only if the shape has exactly four sides and four right angles.

Explanation;

-A rectangle is a 4-sided flat shape with straight sides where all interior angles are right angles (90°). Also opposite sides are parallel and of equal length. Example: A square is a special type of rectangle, here all the four sides are equal.

Therefore; the characteristics of a rectangle include;

-All the properties of a parallelogram apply (the ones that matter here are parallel sides, opposite sides are congruent, and diagonals bisect each other).

-All angles are right angles by definition.

-The diagonals are congruent.

stratosphere: as the altitude increases, the air temperature increases. the stratosphere has a layer of ozone, called the ozone layer. this layer absorbs most of the ultraviolet radiation from sunlight. this results in the stratosphere being warmer.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.