A: AB+BC=DE+EF. Reason:
Solution: the extension line of AB, the reverse extension line of CD intersect G, and the extension line of DE/AF intersect H,
All the angles of a hexagon are equal,
∴∠a=∠abc=∠bcd=∠d=∠afe=∠def= 120,
∴∠GBC=∠BCG=∠HFE=∠HEF=60,
∴△BCD and△△△ Hef are equilateral triangles,
∴BC=BG,EF=EH,∠G=∠H═60,
∴∠A+∠G= 180,∠D+∠G= 180,
∴AG∥DH,AH∥GD,
∴ Quadrilateral AGDH is a parallelogram,
∴AG=DH,
∴AB+BC=DE+EF.