Answer:
The statements we have to rewrite are:
Está prohibido fumar - Se prohíbe fumar
Vendemos periódicos - Se venden periódicos
Hablamos español - Se habla Español
Necesitamos enfermeras - Se necesitan enfermeras
No debes nadar - No se debe nadar
Estamos buscando un auto usado - Se busca un auto usado
Explanation:
Impersonal constructions with "<em>se</em>" don’t reference a specific person, but are used to make general observations about what people do. In impersonal statements there is no obvious grammatical subject, which is what makes them impersonal. In impersonal "<em>se</em>" constructions, verbs are always conjugated in the third person singular. You can use impersonal expressions to talk about how things are done according to custom, rule, or general consensus.
