Which of the following could be used in a concrete slab?

Using steel reinforcements, plastic sheeting, and wire mesh are all common practices in the construction and reinforcement of concrete slabs, which contributes to enhancing their strength and durability.

Steel reinforcements, often in the form of rebar, are crucial for providing tensile strength to the concrete. Concrete is strong in compression but weak in tension; therefore, the presence of steel helps resist bending and cracking, which can occur under load.

Plastic sheeting, on the other hand, is typically used as a moisture barrier. It prevents water from seeping through the slab from the ground below, which can lead to issues like efflorescence or decreased structural integrity over time.

Wire mesh, or welded wire fabric, is another method used to provide reinforcement. Like rebar, it helps distribute loads and minimizes the chances of cracks developing by holding the concrete together as it cures and hardens.

Since all three elements serve vital roles in ensuring the structural integrity and longevity of a concrete slab, they can all be used together, making the comprehensive choice correct.