a) Applications can use the Reporter to report progress
b) The Hadoop MapReduce framework spawns one map task for each InputSplit generated by the InputFormat for the job

c) The intermediate, sorted outputs are always stored in a simple (key-len, key, value-len, value) format
d) All of the mentioned

Answer: d
Explanation: Reporters can be used to set application-level status messages and update Counters.