Twice a day for 20 minutes is the required time to realize that meditation practiced is beneficial for persons physical and mental health.
Meditation practiced helps person in different ways:
Twice a week is very less time and does not make consistency.
Incorrect option.
Several hours at a stretch is not possible for all individual and it is not practical .
Incorrect option.
Twice a day for 20 minutes is the best time and helps individual to practice  meditation.
Therefore, Option C. twice a day for 20 minutes is the best time for mediation.
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