Conoscere= to know, to be familiar with. In the lesson, the inferred context is "We already are familiar with the answers." The hint is the use of the direct object. Sapere=to know (as in facts and specific information). When a form of sapere is followed by an infinitive it means 'to know how to.' Examples: Conosco questo ristorante ( I am familiar with this restaurant); Non so ballare (I do not know how to dance).