根据以下材料，回答题
Insomnia, or "poor sleep", can have bad effects on a person' s health and general well-being.Itcan 21 on both our physical and mental heahh and can lead to other health 22
Insomnia can be traced to many different reasons, but what is 23 to many sufferers is theirinability to relax fully and "switch the mind 24 "
Constant thoughts, 25 around and around in the mind, moving from one 26 to the next,prevent stillness and peace and 27 a sufferer extremely tired.
In order to treat insomnia 28 , it is first necessary to allow a sufferer to re-experience 29 real relaxation feels like.It' s almost as though they' ve forgotten how to relax.Once this has been 30 by the brain, then fast and effective 31 can be made to re-educate the unconscious towardsallowing the person to relax 32 and to allow a natural state of sleep to 33
Hypnotherapy (催眠疗法) is one of the fastest and most effective ways of 34 this goal forlong-lasting results.
Sleeping pills, if used at all, should only be a short-term 35 as their effect is soon reduced andtheir side effects can be deep and far-reaching.
第21题的答案是(　　)