The structural and functional units of liver are called.

The structural and functional units of the liver are referred to as hepatic lobules.

The lobules of the liver, or hepatic lobules, are small divisions of the liver defined at the microscopic (histological) scale.

Each lobule is hexagonal in shape and a portal triad (portal vein, hepatic artery, bile duct) sits at each corner of the hexagon.

Hence the correct answer is option D, i.e., As structural and functional units of liver are called hepatic lobules.