3 Had they prepared the costumes before the director arrived?

3 Had they prepared the costumes before the director arrived?

Переделаем вопрос в пассивный залог. В данном случае действие направлено на "costumes" (костюмы). Получим:

<p>Had the costumes been prepared before the director arrived?</p>

Перевод:

<p>Были ли костюмы подготовлены до прибытия режиссера?</p>

Ответ: Had the costumes been prepared before the director arrived?