The main functions of blood in mammals include:

- Transporting oxygen from the lungs to the body tissues

- Transporting carbon dioxide from the body tissues to the lungs

- Transporting digested nutrients (such as glucose, amino acids, and fatty acids) from the digestive system to the body tissues

- Transporting waste products (such as urea) from the body tissues to the excretory organs (such as the kidneys)

The correct answer is option A - transport excretory materials from tissues