Antonyms are words which have opposite meaning in comparison to the other. Option A)rejoice is correct as the word rejoice means feel or show great joy or delightand the word bemoan means express discontent or sorrow over (something). Both the words are opposite of each other. The other options are wrong as mourn, deplore, and lament mean feel or show sorrow for the death of (someone), typically by following conventions such as the wearing of black clothes,feel or express strong disapproval of (something), and a passionate expression of grief or sorrowrespectively. The correct answer is A)rejoice.