A. Iterative repetition of MapReduce jobs until a desired answer or state is reached.
B. Sequences of MapReduce and Pig jobs. These are limited to linear sequences of actions with exception handlers but no forks.
C. Sequences of MapReduce jobs only; no Pig or Hive tasks or jobs. These MapReduce sequences can be combined with forks and path joins.
D. Sequences of MapReduce and Pig. These sequences can be combined with other actions including forks, decision points, and path joins.

Answer: D