Formerly a palace, the Louvre was made a museum after the French Revolution.
Giải chi tiết:
Đáp án là C. Formerly: trước kia = Previously
Các từ còn lại: Henceforth: từ nay trở đi; Eventually: sau cùng; Frequently: Thường xuyên
Biogas can be utilized for electricity production, cooking, space heating, water heating and process heating.
Population growth rates vary among regions and even among countries within the same region.