What is the inclined beam that supports a roof and runs parallel to the slope of the roof?

The correct answer, which identifies the inclined beam that supports a roof and runs parallel to the slope of the roof, is "rafter." Rafters are structural components that form the framework of a roof, sloping downwards from the ridge or peak to support the roof covering and to aid in transferring weight down to the walls of the building. They are typically arranged in a series, providing support for the roof's load.

In contrast, a beam usually refers to a horizontal structural element that supports vertical loads, while a truss is a framework of beams arranged in triangles that distributes loads across a wider area, often used for roof supports but not specifically inclined or parallel to the roof slope. A purlin serves as a horizontal support for roof sheathing or materials, running across the rafters rather than being parallel to the slope.