Đáp án tham khảo có thể sai: 1a, 2a, 3a, 4a, 5b, 6a, 7a, 8a, 9b, 10a, 11a, 12b, 13d, 14a, 15a, 16d, 17c, 18a, 19a, 20a, 21a, 22a, 23b, 24a, 25b, 26a, 27b, 28d, 29a, 30b, 31a, 34c, 35a, 36a, 37a, 38a, 39a, 40b, 41a, 42a, 43a, 44a, 45a, 46b, 47d, 48a, 49c, 50a. Source: PRN221_FE_SU23_502973