The correct answer is B.
A short story is usually defined as a piece of literature that can be read in one sitting. For this to be achievable, it should have a lenght of no more than 1,000 words.
However, if the story is too short, it is no longer considered a short story but a work of microfiction.
Therefore, the lenght of a short story should be between 200 and 1000 words.