Four of the following five are alike in a certain way and hence form a group. Who among the following one who does not belong to that group?

We have, G sits second to the left of Z. Two persons are sitting between Z and X.  B and X are sitting adjacent to each other. From the above condition, there are three possibilities. Again we have,   The number of persons sitting between Z and B is the same as between Z and A. From the above condition, case1 gets eliminated. Again we have,  Q sits exactly in the middle of W and B.  B sits fifth to the left of A.  W does not sit third to the right of X.  Not more than one person sits between Q and B. From the above condition, case2 gets eliminated. Case 1a shows the final arrangement