A.
N ={ [0],[7],[14] },G/ N ={ N, N [1], N [2], N [3], N [4], N [5], N [6] }
B.
N ={ [0],[7],[14] },G/ N ={ N, N+ [1], N+ [2], N+ [3], N+ [4], N+ [5], N+ [6]}
C.
N ={ [0],[3],[6],[9],[12],[15],[18] },G/ N ={ N, N+ [1], N+ [2], N+ [3], N+ [4], N+ [5], N+ [6]}
D.
N ={ [0],[3],[6],[9],[12],[15],[18] },G/ N ={ N, N [1], N [2]}