Final answer:
To convert 'Los alumnos escribieron quince oraciones' into passive voice, the correct form is 'Quince oraciones fueron escritas por los alumnos,' which translates to 'Fifteen sentences were written by the students' in English.
Step-by-step explanation:
To convert the sentence 'Los alumnos escribieron quince oraciones' into passive voice, we need to ensure that the subject is being acted upon rather than doing the action. This can be achieved by following a structure where the object of the active sentence becomes the subject of the passive sentence, using a form of the verb 'to be' and the past participle of the main verb. In English, the passive voice version of the sentence is:
Quince oraciones fueron escritas por los alumnos.
This translates to 'Fifteen sentences were written by the students' in English. The process involves identifying the original subject ('los alumnos'), verb ('escribieron'), and object ('quince oraciones'), then reconstructing the sentence so that the object comes first, followed by a form of the verb 'to be' (in this case, 'fueron'), and the past participle of the main verb ('escritas'), often including the agent of the action introduced by the preposition 'por' if needed to specify who performed the action.