For Each Intermediate Key, Each Reducer Task Can Emit

For each intermediate key, each reducer task can emit:

A) As many final key-value pairs as desired. There are no restrictions on the types of those key-value pairs (i.e., they can be heterogeneous) .
B) As many final key-value pairs as desired, but they must have the same type as the intermediate key-value pairs.
C) As many final key-value pairs as desired, as long as all the keys have the same type and all the values have the same type.
D) One final key-value pair per value associated with the key; no restrictions on the type.
E) One final key-value pair per key; no restrictions on the type.