The correct option is A All mammals
A) The hepatic portal system is the venous system that returns blood from the digestive tract and spleen to the liver. It is present in mammals.
B) Not all amniotes have a hepatic portal system.
C) The hepatic portal system is found in amphibians and mammals.
D) Higher invertebrates do not have a hepatic portal system.
E) Mammals have a hepatic portal system.
So the correct answer is 'All mammals'.