challenge: What does the term 'gaslighting' refer to in the context of self-help and popular psychology?
  
  A. A method for resolving conflicts in relationships
  B. A technique for building self-confidence
  C. Manipulating a person or group of people, similar to the way the protagonist in the 1944 film 'Gaslight' was manipulated
  D. A type of therapy to treat anxiety disorders
  Answer: 