The small mounds of lymphoid tissue found at the back of the tongue are called:

A. The spleen does not shrink after puberty. It remains an active part of the immune and blood filtration systems throughout life.
B. The thymus (note: it appears misspelled as "Thygus" in the question) is the correct answer. It plays a crucial role in the development of T lymphocytes (T cells) during childhood but begins to shrink and become replaced by fatty tissue after puberty—a process known as involution.
C. The liver does not shrink after puberty. In fact, it continues to grow and function in metabolism, detoxification, and digestion throughout a person’s life.
D. The cisterna chyli is a dilated sac at the lower end of the thoracic duct involved in lymphatic drainage. It does not shrink after puberty and remains functional throughout life.

A. Carotid veins are not the primary veins for receiving lymph from lymphatic vessels. Carotid veins are associated with the head and neck, but they are not the main vessels where lymph drains.
B. Subclavian veins are the correct answer. The lymphatic system drains lymph into the subclavian veins at the junction of the internal jugular vein, where the lymphatic ducts (such as the thoracic duct and right lymphatic duct) empty into the bloodstream.
C. Brachial veins are associated with the upper arm and do not receive lymph from the terminal lymphatic vessels.
D. Pulmonary veins are responsible for carrying oxygenated blood from the lungs to the heart, not lymph.