Correct Answer: A

Rationale: The diaphragm is the correct answer. It is a dome-shaped muscular structure that separates the chest cavity from the abdominal cavity. The diaphragm plays a crucial role in breathing by contracting and relaxing to change thoracic volume during inhalation and exhalation. The sternum is a flat bone in the center of the chest and is not the structure that separates the chest and abdominal cavities. The pericardium is a membrane that surrounds the heart, not involved in separating cavities. The trachea is the windpipe that connects the larynx to the bronchi and is not the structure that separates the chest and abdominal cavities.

Correct Answer: C

Rationale: A genetic disorder caused by a mutation on the X chromosome is termed a sex-linked recessive disorder (Option C). This type of disorder is more commonly seen in males due to their single X chromosome, making them more vulnerable to X-linked mutations. Females have two X chromosomes, providing a protective effect against X-linked disorders.\n- Autosomal dominant disorders (Option A) result from a mutation in one copy of a gene on non-sex chromosomes (autosomes) and are not specifically related to the X chromosome.\n- Autosomal recessive disorders (Option B) occur due to mutations in both copies of a gene on autosomes, not on the X chromosome.\n- Sex-linked dominant disorders (Option D) are rare and lead to more severe symptoms in males as they only require one copy of the mutated gene on the X chromosome to express the disorder. However, this is not the term for a genetic disorder caused by an X chromosome mutation.

Correct Answer: B

Rationale: Arteries are the blood vessels responsible for carrying oxygenated blood away from the heart to the rest of the body. Their thick, muscular walls allow them to withstand high pressure and efficiently transport blood to various tissues and organs throughout the body. Veins (choice A) carry deoxygenated blood back to the heart, capillaries (choice C) facilitate the exchange of nutrients and waste products between the blood and tissues, and venules (choice D) are small blood vessels that collect blood from the capillaries and gradually converge into veins.

Correct Answer: A

Rationale: In ecology, a closed system is one that does not exchange matter with its surroundings but can exchange energy. This means that while energy can enter or leave the system, the amount of matter within the system remains constant. Option A correctly defines a closed system in ecology. Choices B and C are incorrect as a closed system does not exchange matter or energy. Option D is unrelated to the concept of a closed system in ecology.

Correct Answer: A

Rationale: A) Golgi apparatus: The Golgi apparatus is responsible for modifying, sorting, and packaging proteins into vesicles for secretion outside the cell or for use within the cell. It acts as a distribution and shipping department for the cell, ensuring proteins are properly processed and sent to their correct destinations like the extracellular space. Golgi apparatus is the correct answer because it directly handles the packaging and secretion of proteins. B) Mitochondria: Mitochondria are known as the powerhouse of the cell and are responsible for generating energy in the form of ATP through cellular respiration. They are not involved in packaging and secreting proteins into the extracellular space. C) Ribosomes: Ribosomes are responsible for protein synthesis, where they translate mRNA into proteins. They are not involved in packaging and secreting proteins into the extracellular space. D) Endoplasmic reticulum: The endoplasmic reticulum (ER) plays a role in protein synthesis and folding, but it is the rough ER specifically that is involved in synthesizing proteins that are then transported to the Golgi apparatus for further processing and packaging. The Golgi apparatus is primarily responsible for packaging and secreting proteins, making it the correct answer for this question.