You will be given a definition of a task first, then some input of the task.
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".

[header] How to fit a mortice deadlock [title] Measure where the lock will fit on the door. [step] As a guide, the height of your lock should be about 1 metre high. [title] Using your measurement, mark out both the top and bottom of the latch. <sep> (A) [step] To determine the height, measure out 1 metre high. It's easier to fit a mortice lock and reverse the measurement before final locking. (B) [step] That is, hold them straight with your fingers pointing outwards, while you measure them out on the outside. And that means the edges of the lock should match the lines on each side. (C) [title] Weigh the weight of the mortice (or combination lock) against the weight of the lock. [title] Have them fit together by applying two coats of interior caulk to their sides. (D) [title] Measure and mark out a vertical central line. [step] This will be your guide when drilling.
Output:
D