Check the pattern: 4 to 9 is +5, 9 to 14 is +5, 14 to 18 is +4 (wrong!), 18 to 24 is +6, 24 to 29 is +5. The pattern should be adding 5 each time. The term 18 breaks this pattern because 14 + 5 = 19, not 18. If 18 were replaced with 19, the series would be consistent: 4, 9, 14, 19, 24, 29. Option C (18) is indeed the wrong term.