When pouring a concrete slab, which of the following tools is used to finish the concrete?

The trowel is the correct tool for finishing concrete slabs because it is specifically designed to smooth and level the surface of the concrete after it has been poured. A trowel allows for precise control, enabling the worker to create a flat, even surface and achieve a desired texture. This tool is essential for creating a professional finish, as it can be used to work the concrete surface to remove imperfections, create a polished look, and prepare it for any further treatment or sealing.

While other tools mentioned serve different important functions in the concrete pouring process, they do not fulfill the finishing role as effectively as the trowel. For example, a tamper is typically used for compacting the soil or sub-base before the concrete is poured, ensuring stability and reducing voids. The vibrator is employed to eliminate air bubbles and help the concrete settle, which is critical for achieving strength and durability but does not contribute to the surface finish itself. A grasshopper is not a standard tool used in concrete finishing. Each tool plays its role in the overall process, but the trowel is specifically focused on achieving the smooth finish characteristic of a well-poured concrete slab.