Preposiciones con verbos pasivos

[A] Activa:   Dufy painted this picture > Pasiva:   This picture was painted by Dufy ; Activa:    What makes these holes? > What are these holes made by? ; Smoke filled the room > The room was filled with smoke ; Paint covered the lock > The lock was covered with paint. [B] Activa: We must write to him > Pasiva: He must be written to ; Activa: You can play with these cubs quite safely > Pasiva: These cubs can be played with quite safely ; Activa: They threw away the old newspapers > Pasiva: The old newspapers were thrown away ; Activa: He looked after the children well > Pasiva: The children were well looked after.

[[A] El agente, cuando se menciona, va precedido por by; pero a veces se trata con materiales utilizados, no con agentes, y se utiliza with. [B] Cuando una combinación de verbo + preposición + objeto se pone en la voz pasiva, la preposición permanecerá inmediatamente después del verbo; lo mismo ocurre con combinaciones de verbo + preposición/adverbio.]