Sorry I did n't see Ron's earlier post asking whether the question is from GMAT prep or somewhere else.
@Tim, You might interpret my praise of Ron's Skills at explaining SC problems,But I did not try to "flatter" him so that he answers my query ,going against Forum rules. :)
Thanks for your time for answering though.You guys are doing great job . Am not flattering while I say so.I really mean it :)