Đáp án tham khảo có thể sai: 1a, 2b, 3a, 4b, 5b, 6b, 7c, 8c, 9a, 10a, 12b, 13b, 14d, 15a, 16a, 17d, 18a, 19a, 20d, 21d, 23c, 24bcd, 25a, 27c, 28b, 29a, 30a, 31a, 32c, 33c, 34a, 35d, 36a, 37c, 38b, 39a, 40d, 41a, 42c, 43a, 44abc, 45d, 46b, 47a, 49c, 50d, 51c, 52a, 53a, 54d, 55c, 56a, 57a, 58ad...