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".

There are people at the top of a snowy hill on tube rings. suddenly the people <sep> (A) grabbing snow mobiles get stuck on rails on the sides of the tubes. (B) lift up their backpacks and go down the slope. (C) stand still, then start rolling down the slope on their tube. (D) start riding down the hill.
Output:
D