31. 以下哪項不是有效的SQL指令？
(A)SELECT * FROM Lawyers WHERE firmName LIKE '% and %';
(B)SELECT COUNT(*) FROM Firms WHERE employees ＜ 100;
(C)SELECT firmLoc, COUNT(*) FROM Firms WHERE employees ＜ 100;
(D)SELECT firmLoc, COUNT(*) FROM Firms WHERE employees ＜ 100 GROUP BY firmLoc;