Correct Answer: A

Rationale: The correct answer is A: Femur. Long bones are characterized by their elongated shape, with examples including the femur, humerus, and tibia. These bones are essential for support, movement, and bone marrow production. Choice B, 'Ribs and cranial bones,' consists of flat bones, not long bones. Choice C, 'Sesamoid,' refers to small bones embedded within tendons and do not fall under the category of long bones. Choice D, 'Vertebrae and hip bones,' includes irregular bones that provide structural support and protection for vital organs, but they are not classified as long bones.

Correct Answer: C

Rationale: The correct answer is C: To exchange gases. The primary function of the respiratory system is to facilitate the exchange of gases, specifically oxygen and carbon dioxide, between the body and the environment. This process is essential for cellular respiration, where oxygen is taken in and carbon dioxide is removed. Choices A, B, and D are incorrect. Digesting food is primarily the function of the digestive system, transporting nutrients is the role of the circulatory system, and regulating body temperature is primarily managed by the integumentary system and the nervous system, not the respiratory system.

Correct Answer: C

Rationale: The correct answer is 'C: molarity.' Molarity is the concentration unit that depends on pressure. In molarity, the concentration of a solution is expressed as the number of moles of solute per liter of solution. This means that changes in pressure can affect the volume of the solution and consequently the concentration. Choices A and B, ppm (parts per million) and ppb (parts per billion), respectively, are independent of pressure variations as they are based on mass ratios. Therefore, molarity is the only concentration unit listed that is directly influenced by changes in pressure.

Correct Answer: A

Rationale: The correct answer is A: Femur. Long bones are characterized by their elongated shape, with examples including the femur, humerus, and tibia. These bones are essential for support, movement, and bone marrow production. Choice B, 'Ribs and cranial bones,' consists of flat bones, not long bones. Choice C, 'Sesamoid,' refers to small bones embedded within tendons and do not fall under the category of long bones. Choice D, 'Vertebrae and hip bones,' includes irregular bones that provide structural support and protection for vital organs, but they are not classified as long bones.

Correct Answer: D

Rationale: Ventilation is the correct answer as it specifically refers to the mechanical process of breathing air in and out of the lungs. Diffusion (choice A) is the movement of molecules from an area of high concentration to low concentration, not related to the mechanical act of breathing. Perfusion (choice B) is the process of blood flow through the tissues and organs, not directly related to breathing mechanically. Respiration (choice C) involves the exchange of oxygen and carbon dioxide at the cellular level, different from the mechanical act of breathing.