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In Group 2, the two tones in each pair are separated by a major 3rd (which is equal to four semitones).

You will notice that with the major third, visual proximity is considerably reduced.  While we would be less inclined to visualize it this way, it becomes possible to imagine a C-E sequence as a descent; i.e. as a counter-clockwise movement.  This possibility is corraborated in our hearing of it. Notice that not all of the pairs sound like they are ascending.