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: And introduction comes onto the screen for a video about how to remove a bike chain. a person sitting next to a bike <sep> (A) runs his hands around the chain on it. (B) is assembling a handle. (C) is about to look at the chain from which it was removed, and he starts swinging his legs around in circles. (D) demonstrates how to remove and replace a bike chain using a small tool.
Output:
D