Sorry I'm rubbish at explaining NVR in writing (I find it much easier to demonstrate it) the theme is the thick bold line. Please excuse my terminology!!! In the first column the thick line is horizontal, then point up to the right, then point up to the left, so horizontal, point up to the right, up to the left is the pattern, if the first column were to continue we would have a horizontal line next then point up to the right etc etc, the second column starts with point up to the left (which was the last on the previous column) so then we get horizontal then point up to the right, the final column starts with point up to the right, so then comes point up to the left (i.e c) then horizontal. The shapes themselves are a red herring, the key is the positioning of the thick line.
