Q: 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". 
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.
A:
D