What do TEU and FEU mean?

A、TEU= Forty-foot equivalent unit; FEU= Twenty-foot equivalent unit;
B、TEU= Twenty-foot equivalent unit; FEU= Forty-foot equivalent unit;
C、TEU= Fourteen-foot equivalent unit; FEU= Twelve-foot equivalent unit;
D、TEU= Twelve-foot equivalent unit; FEU= Fourteen-foot equivalent unit