Which of the following words is stressed on the last syllable? compras piscina comercial montañas

Ireally, really need with this asap. i don't understand spanish prepositions and when they should be used. the questions are:fiesta con juan el fin de semana pasado. el parque está casa. es una lástima que haya tantos lago. el jefe quiere inmediatamente. the answers can be one of the following: en, con, de, a i will award !