Answer:
See Explanation below.
Step-by-step explanation:
What the workers can do to ensure the patio is truly rectangular, before pouring the concrete, is <u>to measure the length of the sides of the patio.</u>
This requires full knowledge of the physical properties of a rectangle.
The opposite sides of a rectangle (the two sides which go in the same direction or which are parallel to each other) are equal in length and one set of parallel sides must be longer than the other set of parallel sides.
These are the conditions that the patio must satisfy, to be truly rectangular.
Once the workers have made sure of this, they can go ahead and pour the concrete.