For Each Input Key-Value Pair, Mappers Can Emit

For each input key-value pair, mappers can emit:

A) As many intermediate key-value pairs as designed. There are no restrictions on the types of those key-value pairs (i.e., they can be heterogeneous) .
B) As many intermediate key-value pairs as designed, but they cannot be of the same type as the input key-value pair.
C) One intermediate key-value pair, of a different type.
D) One intermediate key-value pair, but of the same type.
E) As many intermediate key-value pairs as designed, as long as all the keys have the same types and all the values have the same type.