Which tool is primarily used for cutting lumber at precise angles?

The miter saw is specifically designed for making precise angled cuts, which is essential for tasks such as framing and molding work. This tool allows the user to set the blade at various angles, making it ideal for creating accurate bevels and miters on the ends of boards. The fixed base and pivoting blade provide stability and precision, allowing for clean cuts that are crucial in finishing and detailing applications.

In contrast, a circular saw, while versatile and useful for various straight cuts, does not offer the same degree of angle adjustment or stability for precise cuts. A jigsaw is better suited for intricate cuts and curves rather than straight angle cuts, and a band saw is typically used for cutting thicker materials or making curved cuts rather than for precision angle work. Thus, the miter saw stands out as the optimal choice for cutting lumber at precise angles, making it the correct answer.