In a MapReduce Job, the Reducer Receives All Values Associated

In a MapReduce job, the reducer receives all values associated with same key. Which statement best describes the ordering of these values?

A) The values are in sorted order.
B) The values are arbitrarily ordered, and the ordering may vary from run to run of the same MapReduce job.
C) The values are arbitrary ordered, but multiple runs of the same MapReduce job will always have the same ordering.
D) Since the values come from mapper outputs, the reducers will receive contiguous sections of sorted values.