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