Several million visit Barcelona every year
A chocolate cake was backed by my mother
Barcelona is visited every year by several million
passive voice
The room is not _______ cleaned by my sister.
The car has been washed in the yard
The bank was robbed by thieves
Affirmative formula Passive Voice in past continuous
The house was being soiled by the dog
The passive voice is a verbal construction in some languages by which the subject is presented as passive, while the action performed by the verb is performed by a complement and not by the active subject of the verb.
Varios millones visitan Barcelona cada año
being
Barcelona es visitada cada año por varios millones
La casa estaba siendo ensuciada por el perro
El coche ha sido lavado en el patio
Subject + was/were + verb in past participle
Una tarta de chocolate fue horneada por mi madre
El banco fue atracado por unos ladrones