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Ustedes necesitan hablar con el profesor de economía.
¿Quién necesitan hablar? - Quién is constantly inferred as particular however necesitan suggests a gathering of individuals (plural), so the verb conjugation needs to concur with quién. Doing as such, you would be asking "Who needs to talk?". On the off chance that you needed to signify "Whom do you all need to converse with?", include con toward the question's start; the conjugation relies on upon the pronoun; necesitan infers ustedes necesitan or ellos necesitan, it's vague however it's totally right. In the event that you need to be particular, include the pronoun toward the question's end, e.g. ¿Con quién necestian hablar ellos?. Credit for conjugating two verbs together accurately. :)
¿Qué enseña la clase de economía? Alright
¿Dónde llegan ustedes? - I assume you needed to say "achieve" as in coming to somebody, isn't that so? Else I don't perceive how this inquiry would be identified with the postive sentence. On the off chance that that is the situation, the right question would sound practically the same as 4a. In the event that that is not the situation, then change dónde for a dónde, since llegar suggests coming to a destination, which needs a.
¿Toman la clase de economía? OK
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