Definition: 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: A man and a woman wearing roller blades kneel facing each other on a basketball court. a dog <sep> (A) pushes a ball down a stairs. (B) runs by the man and woman. (C) does flips on the sand. (D) runs behind the couple while the two continue skating.
Output:
B