Answer:
5.
b. She can measure the opposite sides. If they are congruent, then the bookshelf is in the shape of a parallelogram. Then she can measure the diagonals. If they are congruent, then the bookshelf is rectangular.
6.
c. Square
Explanation:
5. Let us consider the properties of a parallelogram,
1. Opposite sides are congruent and parallel to each other
2. Diagonals of parallelogram bisect each other
3. If one angle of a parallelogram is 90 degrees then all the angles are 90 degrees.
In case of a rectangle, it obeys all the properties of parallelogram except, one thing, the diagonals of a rectangle are equal in measure.
So if the carpenter finds out that the diagonals of the bookshelf are congruent and the opposite sides are congruent then it is a rectangle.
6. If the diagonals of a parallelogram are perpendicular and congruent then it is a square because in a square, both the diagonals are congruent to each other and they bisect each other at right angles. Therefore, the most descriptive name possible is a square.