Final answer:
The correct answer is d. Square, which is used in woodworking to mark and measure 90-degree angles. Other options like a ruler, protractor, or compass do not serve the same fixed angle function as the square.
Step-by-step explanation:
The correct answer to the question "Used mainly for woodworking, this is a fixed, 90-degree angle" with options a. Ruler, b. Protractor, c. Compass, d. Square, is d. Square.
In woodworking, a square is an essential tool used to mark and measure materials at a precise 90-degree angle to ensure accuracy in the construction of objects.
There are various types of squares used in woodworking, such as the try square, framing square, and combination square, all of which are designed to provide a perfect right angle.
The ruler is a straight measuring tool, but it does not specifically mark 90-degree angles. A protractor is used to measure and draw various angles but is not fixed at 90 degrees. A compass is a drawing tool used to mark out circles and arcs, not for creating fixed angles.
Thus, the correct answer is d. Square as it is specifically designed to produce and verify 90-degree angles in woodworking projects.