Применим протокол А. Необходимо вставить пропущенное слово в предложение.
Проанализируем предложение: "The girls were hungry because it was ..."
В первом абзаце есть предложение: "It was lunch time when we arrived home and we were hungry."
Следовательно пропущенное слово - lunch.
Вставим его в предложение: The girls were hungry because it was lunch.
Ответ: The girls were hungry because it was lunch.