OIL, COAL, AND NATURAL GAS ARE ………… .

6. - 3 DE THI HK 2 ANH LOP 11 3 DE THI THU HK II LOP 11 NH 20132014 TU LUAN
3 DE THI HK 2 ANH LOP 11 3 DE THI THU HK II LOP 11 NH 20132014 TU LUAN

6. Oil, coal, and natural gas are ………… .