1) ZYXW/W X YZ / Z Y XW / WXYZ→ follows a pattern. 2) ZYX W W Y YZZ X XWWXYZ→ doesn't follow a pattern 3) ZYX W W X YZZ Z XWWXYY→ doesn't follow a pattern 4) ZYX X W Y YZZ Z XWWXYW→ doesn't follow a pattern Hence, W X Y Z is the correct set of letters.