There is a multiple choice test paper with a total of 6 sub-questions. The scoring criteria are: 8 points for a correct answer, 0 points for a wrong answer, and 2 points for a non-answer. A classmate scored 20 points, but he? ['Answer at least one question correctly.', 'There are at least three sub-questions.', 'Answer at least three small questions correctly.', 'Two wrong answers.']