Regarding hypnosis, which of the following statements is true?
A. Hypnosis is a sleep state in which the subjects are partially aware of their actions and able to perform many activities not normally carried out during sleep.
B. Hypnosis was introduced by the Austrian physician Karl Zener.
C. Hypnosis is an altered state characterized by narrowed attention and increased openness to suggestion.
D. Hypnosis is characterized by brain wave patterns similar to sleep.