Concept:The sequence should follow a regular pattern of increasing differences.Explanation:Starting from 503, add consecutive numbers: +1,+2,+3,+4,+5.So the correct sequence should be 503,504,506,509,513,518.The given sequence is 503,508,506,509,513,518.Here, 508 does not fit the pattern; it should be 504.Hence, 508 is the wrong term.Answer:The odd term is 508.