The correct answer is A). Enforced.
The best synonym for the word obligatory as it is used in this excerpt from Goines's "Let Sleeping Dogs Lie" is enforced.
Enforced means “to force obedience to something”. In the text “…obligatory public incineration…” indicates that the person must do what it is refered.
“Let Sleeping Dogs Lie” was written by David L. Goines. He was born in Grant Pass, Oregon and is an American calligrapher and author.