1. Tu sabes el precio del vestido?
This sentence means - Do you know what the price of this dress is? Both saber and conocer are translated the same into English (=to know), but saber is to know with the meaning of actual knowledge (I know math well), whereas conocer means that you know someone or someone's work (I know Maria well).
2. Usted conoce a mi hermana Maria, no?
Here you have to use conoce because the question is asking - Do you know my sister Maria? Just apply the appropriate suffix for usted (third person singular), and there you will have your correct answer.
3. Nosotros sabemos hacer windsurf.
This sentence means - We know how to windsurf. Obviously you would use the verb 'saber' here because you want to show that you have the knowledge of doing something, not that you know a particular person.
4. Yo se donde esta la corbata azul.
This sentence means - I know where the blue tie is. Naturally, you would use the verb 'saber' here as well to denote that you know the location of that particular thing you are looking for, rather than a person or their work.
5. Ellas conocen los libros de Carlos Fuentes?
The sentence means - Do they know novels by Carlos Fuentes? Here, you would use the verb 'conocer' meaning that they are familiar with this author's works, rather than 'saber' which wouldn't mean anything in this context.
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Answer:</h2>
C. nos
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Explanation:</h2>
An indirect object pronoun is used to tell us<em> to whom</em> or <em>for whom</em> something is done. In this case, I went to school to our first class of the year, so the profesor talked about the rules of the University. Since the action is being performed for us, that is, he talked to a group of students, then we choose the indirect object pronoun that matches the first person plural, which is nos. Therefore:
<em>Ayer fui a nuestra primera clase del año y el profesor </em><em>nos</em><em> habló de las reglas de la universidad</em>
Museo es la respuesta correcta
Les compran regalos a sus padres:)