What type of bracing runs parallel to the ceiling joist to keep rafters from spreading apart?

The correct choice is collar tie bracing, which serves an important function in roof construction. Collar ties are horizontal members that are installed between the opposing rafters, typically near the top third of the rafter height, and run parallel to the ceiling joists. Their primary purpose is to prevent the rafters from spreading apart at the top and to provide lateral support.

By connecting the rafters together and resisting outward forces, collar ties help maintain the structural integrity of the roof. This is especially crucial in scenarios where the roof experiences heavy loads such as snow or strong winds, as it helps to keep the shape of the roof intact. Additionally, collar ties can also contribute to the overall rigidity of the roof system, preventing sagging over time.

Other types listed, such as rafter bracing, strut, and gable bracing, serve different purposes within the structural framework but do not provide the same function as collar ties. Rafter bracing typically acts diagonally to support the rafters, struts are used to transfer loads vertically, and gable bracing helps stabilize the gable ends of a structure. Thus, collar tie bracing is specifically designed to address the issue of rafter spreading and plays a crucial role in maintaining the roof