Final answer:
The most appropriate tool for determining the grade, or slope, for a concrete slab is a level, as it is specifically designed to ensure a flat or properly angled surface, which is crucial for drainage and stability.
Step-by-step explanation:
When working on a construction project, such as setting the grade for a concrete slab, it is critical to use the right tools for accuracy and efficiency. Each tool mentioned serves a different purpose in construction and landscaping. The tools in question here are the tape measure, tamper, strike-off board, and level. For measuring distances, such as the width of a street or the length of a basketball court, a tape measure is an excellent choice due to its flexibility and the ability to measure in both customary and metric units.
However, when the task is to determine the grade, or slope, for a concrete slab—ensuring that it is flat or angled correctly for proper drainage—a level is essential. A level can be used to ensure that the concrete slab is being laid out flat and true. While a tape measure is useful for measuring linear distances, it cannot alone determine the slope or levelness of a surface. Hence, it is clear that the most appropriate tool for determining grade for a slab would be a level.