Explanation:
The correct answer is:

E. Excretion of urea from the blood

While the liver plays a crucial role in the formation of urea (a process known as deamination of amino acids) and detoxification, it does not excrete urea directly. The kidneys are responsible for the excretion of urea from the blood. The liver, however, converts excess amino acids into urea, which is then filtered out by the kidneys.

The other options are functions of the liver:
- Regulation of blood sugar (by storing and releasing glucose as needed),
- Storage of iron (in the form of ferritin),
- Formation of bile (to aid in digestion),
- Breakdown of excess amino acids (through deamination).