Which of the following are part of the first line of defense against invaders: (select all that apply)

A. Pharyngeal tonsils (also called adenoids) are located in the nasopharynx, not at the back of the tongue.
B. Palatine tonsils are located on either side of the back of the throat, not at the back of the tongue.
C. Lingual tonsils are small mounds of lymphoid tissue located at the base of the tongue, and they help protect the body from pathogens entering through the oral cavity.
D. Adenoids are another term for the pharyngeal tonsils, which are located in the nasopharynx, not at the back of the tongue.

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.