Where does a MapReduce job store the intermediate data output from Mappers?

A.
On the underlying filesystem of the local disk machine on which the JobTracker ran.

B.
In HDFS, in the job’s output directory.

C.
In HDFS, in temporary directory defined mapred.tmp.dir.

D.
On the underlying filesystem of the local disk of the machine on which the Mapper ran.

E.
Stores on the underlying filesystem of the local disk of the machine on which the Reducer.

Explanation:
The mapper output (intermediate data) is stored on the Local file system (NOT
HDFS) of each individual mapper nodes. This is typically a temporary directory location which can
be setup in config by the hadoop administrator. The intermediate data is cleaned up after the
Hadoop Job completes.

Reference:
24 Interview Questions & Answers for Hadoop MapReduce developers , Where is the
Mapper Output (intermediate kay-value data) stored ?