Правильно ли я составила предложения? если нет, исправить 1) what is the most common traditions of christmas? 2) in what century people decorate their houses by fruits, candy, nuts or paper ornament? 3) when christmas trees were made much safer? 4) who have decorated trees through the season? 5) what tress became popular in the mid-1900s? заранее )
5. Возможно опечатка. Если имеются ввиду деревья, то не tress, а trees.
В остальном всё правильно.