In a Large MapReduce Job with M Mappers and N

Multiple Choice

In a large MapReduce job with m mappers and n reducers, how many distinct copy operations will there be in the sort/shuffle phase?

A) mXn (i.e., m multiplied by n)
B) n
C) m
D) m+n (i.e., m plus n)
E) m n (i.e., m to the power of n) (i.e., m to the power of n)