What classes of sustantivos is: alegría

Ineed someone who has either taken the unidad 9 prueba_gramática quiz, or at the very least, knows the passive voice in spanish to answer this question. completa la oración con la voz pasiva con se. the cake was eaten. la torta. there are no answer choices provided, you must simply fill in the blanks. 'se comieron' and 'venta de' are incorrect answers, so do not answer with either.

Fill the blank with a la, a las, a los, or al. mi padre .

Ineed with spanish because i suck at it. is this right?