The first one is special, for two reasons: 1) as stated by others earlier: it´s the only one that isn´t special The next reason states it more clearly imo. 2)

The first one is special, for two reasons: 1) as stated by others earlier: it´s the only one that isn´t special The next reason states it more clearly imo. 2) the first symbol differs from the other four symbols in exactly 1 way; the other symbols differ from each other in 2 ways.