Learn French: Quelle pyramide a été construite par le roi ?

We use the passé composé of the verb être—which is a été (has been)—and add the past participle of our main verb, construire (to build). Together, a été construite translates to "was built" or "has been built."

Why does construite end with an -e? Isn't the auxiliary verb avoir (a)?

The true auxiliary verb for the passive voice is always être. Here, a été is simply the passé composé form of être. Because we are using être, the past participle construite must agree with the subject of the sentence. Since pyramide is feminine singular, we add an -e.

Why do we use par to say "by the king"?

In the passive voice, the person or thing doing the action is usually introduced by par. You might occasionally see de used to mean "by," but that is mostly reserved for verbs describing states of being or emotions (like being loved or known). For a physical action like building, we use par.

Could I ask this using est-ce que, like Quelle pyramide est-ce qu'a été construite...?