Process of elimination is a logical method to identify an entity of interest among several ones by excluding all other entities.
In educational testing, the process of elimination is a process of deleting options whereby the possibility of an option being correct is close to zero or significantly lower compared to other options. This version of the process does not guarantee success, even if only 1 option remains since it eliminates possibilities merely as improbable.
The method of elimination is iterative. One looks at the answers, determines that several answers are unfit, eliminates these, and repeats, until one cannot eliminate any more. This iteration is most effectively applied when there is logical structure between the answers - that is to say, when by eliminating an answer one can eliminate several others. In this case one can find the answers which one cannot eliminate by eliminating any other answers and test them alone - the others are eliminated as a logical consequence; this is the idea behind optimizations for computerized searches when the input is sorted - as, for instance, in binary search.
In order for the method to work it is necessary to list all possible, even improbable, possibilities. Any omissions render the method invalid as a logical method.