Đáp án tham khảo, có thể sai: 1a, 2a, 3a, 4a, 5d, 6c, 7b, 8a, 9d, 10a, 11e, 12b, 13d, 14b, 15c, 16ac, 17c, 18bd, 19abf, 20d, 21b, 22cd, 23d, 24d, 25c, 26c, 27b, 28a, 29b, 30d, 31a, 32d, 33d, 34ab, 35d, 36a, 37a, 38d, 39b, 40c, 41a, 42d, 43c, 44bcd, 45b, 46c, 47a, 48c, 49bc, 50d, source ...