What is the effect of an unreliable narrator? what are the characteristics of an unreliable narrator, and how does this add interest to a story?

In literature, an unreliable narrator is the one that distorts, keeps, contradicts, or avoids telling certain information to confuse, to lie to other characters, or to make the reader wonder whether something may be true or not.  

The use of an unreliable narrator turns the reader into an active one, who seeks to dissect and identify the instances in which the narrator may be unreliable.

wheres the options? i dont think this can be solved with out the options

the time most likely will repeat, in the story.