The Method of Residues Is Designed to Deal with Situations

The method of residues is designed to deal with situations where

A) a cause that operates within a complex set of effects is sought and while the exact variable cannot be isolated it is possible to manipulate it experimentally.
B) a cause is sought for a similar effect occurring in disparate circumstances and the major candidates for possible causes can be eliminated or produced experimentally.
C) a cause that operates within a complex set of effects is sought and many but not all of the contributing causes are already known.
D) a cause, the necessary cause of an effect, is sought-investigators wish to confirm that an effect simply cannot happen without this antecedent event.