I believe the correct answer is Ayer supe que Luciana se va. In Spanish, there are some words which indicate which tense should be used. Ayer, meaning yesterday, is one of those words - it is usually used with preterite. So we have to choose between conoci and supe, because both are preterite forms (conocia and sabia are imperfect and should not be used with ayer). Saber means to learn, find out, whereas conocer means to meet someone, or know something. In this case, it's better to use the verb saber and its form supe.
