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