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