4. John scored 93 points in a certain AHSME competition. If the old scoring method were still valid, he would have scored only 84 points with the same answers. The number of questions he did not answer is (the new scoring standard is 5 points for a correct answer, 0 points for a wrong answer, and 2 points for unanswered questions. Under the old scoring method, starting from 30 points, 4 points are added for each correct answer and 1 point is deducted for each wrong answer, with no points added or deducted for unanswered questions) (Note: The AHSME competition has a total of 30 questions)
A. 6
B. 9
C. 11
D. 14
4. B Let John answer $x$ questions correctly, $y$ questions incorrectly, and leave $z$ questions unanswered, then we have $5 x+0 y+2 z=93,30+4 x-y+0 z=84, x+y$ $+z=30$, solving these equations yields $z=9$.