Silence is mandatory for meditation to be effective.

A. compulsory

B. optional

C. voluntary

D. permissive

Answer: Option A

Solution(By Examveda Team)

compulsory : required by law or a rule; obligatory.
optional : available to be chosen but not obligatory.
voluntary : done, given, or acting of one's own free will.
permissive : allowing or characterized by great or excessive freedom of behaviour.
mandatory : required by law or mandate; compulsory.

Synonym of mandatory is compulsory