Instructions: In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".
Input: [header] How to install sliding barn doors [title] Measure and cut two lengths of mounting board for each barn door. [substeps] The boards should be as long as the doors and about 1 inch (or 4 cm) wider than the track. [title] Attach the mounting boards to the top and bottom of the doorway using drywall anchors and ensure that the mounting boards run straight along the doorway. <sep> (A) [title] Mount the 3 mounting boards to the door frame in a set row. [substeps] Lift and push, holding the door frame for support and lifting. (B) [title] Measure and cut two lengths of track for each barn door. [title] Use joint brackets to attach sections of track as needed. (C) [title] Mark where you want to mount your sliding barn door using mounting hardware. [substeps] Measure the door of the barn and mark a spot along the plywood where the track stops. (D) [title] Patch any cracks and gaps in the doorway with drywall compound. [substeps] Drywall compounds of course must be obtained and repaired at a hardware store.
Output:
B