The correct answer is option 'C', liver. Chloragogen cells in Pheretima, which is an earthworm, perform a similar function to the vertebrate liver. Let's understand the functions of both chloragogen cells and the liver in detail.

Chloragogen Cells:
1. Found in Pheretima (earthworms) and some other invertebrates.
2. These cells are distributed throughout the body cavity of the earthworm.
3. They are involved in the metabolism of glycogen and fats.
4. Chloragogen cells store glycogen, which can be used as an energy reserve.
5. They are also responsible for synthesizing, storing, and breaking down fats.

Liver:
1. The liver is a vital organ found in vertebrates, including humans.
2. It is located in the upper right side of the abdomen, below the diaphragm.
3. The liver performs numerous functions in the body, including:
a) Metabolism: The liver is involved in carbohydrate, lipid, and protein metabolism. It helps regulate blood sugar levels, synthesizes cholesterol, and converts excess nutrients into storage forms.
b) Detoxification: The liver detoxifies harmful substances, such as drugs, alcohol, and toxins, by breaking them down or converting them into less harmful forms.
c) Storage: The liver stores vitamins (A, D, E, K), minerals (iron and copper), and glycogen.
d) Production: It synthesizes bile, a substance that aids in the digestion and absorption of fats.
e) Blood Regulation: The liver filters and processes blood, removing old or damaged blood cells and producing blood clotting factors.
f) Immune Function: It plays a role in the immune system by removing bacteria, viruses, and other foreign substances from the bloodstream.
g) Hormone Regulation: The liver regulates hormone levels by metabolizing and eliminating hormones from the body.

Similarities between Chloragogen Cells and the Liver:
1. Both chloragogen cells in Pheretima and the liver in vertebrates are involved in metabolism.
2. They both store energy reserves in the form of glycogen.
3. Both chloragogen cells and the liver are responsible for synthesizing and breaking down fats.

Therefore, the function of chloragogen cells in Pheretima is similar to that of the vertebrate liver.

Chloragogen cells, also called as y cells, are cells in annelids that function similarly to the liver invertebrates. The cells store glycogen and neutralize toxins, are yellowish in colour due to the presence of yellow granules called chloragosomes and are present in coelomic fluid of some annelids.