Which of the following is an example of a long bone in the human body?

Correct Answer: B

Rationale: The correct answer is B, Femur. The femur is the longest and strongest bone in the human body, located in the thigh region. Long bones are characterized by their elongated shape, such as the femur, which provides support, strength, and mobility. Choices A, C, and D are incorrect because carpal bones (A) are short bones found in the wrist, tarsal bones (C) are short bones found in the ankle, and metacarpal bones (D) are classified as long bones, but they are shorter than the femur and mainly found in the hand.

Correct Answer: C

Rationale: The correct answer is C: GABA (gamma-aminobutyric acid). GABA acts as an inhibitory neurotransmitter that reduces neuronal activity, thus preventing overexcitation. Acetylcholine (choice A) is involved in muscle control and cognitive function, but it is not primarily responsible for slowing down neuronal activity. Dopamine (choice B) plays a role in reward-motivated behavior and motor control, rather than inhibiting neuronal firing. Serotonin (choice D) is involved in mood regulation, sleep, and appetite but does not primarily slow down neuronal activity to prevent overexcitation.

Correct Answer: A

Rationale: The pleurae play a crucial role in compartmentalizing and lubricating the lungs. The pleura is a double-layered membrane that surrounds the lungs and lines the chest cavity. This double-layered structure reduces friction between the lungs and the chest wall during breathing movements, allowing smooth expansion and contraction of the lungs. Options B, C, and D are incorrect. Option B, 'To facilitate the flow of air,' is incorrect because while the pleurae are involved in the respiratory process, their primary function is not to directly facilitate the flow of air. Option C, 'To produce mucus,' is incorrect as the production of mucus is not a primary function of the pleurae. Option D, 'To serve as the passageway for air,' is incorrect as the passageway for air refers to the air passages like the trachea and bronchi, not the pleurae. Therefore, option A is correct as it accurately describes the function of the pleurae.

Correct Answer: D

Rationale: The skin is the largest organ in the human body. It covers the entire body, serving as a protective barrier against pathogens, UV radiation, and physical damage. Additionally, the skin plays a crucial role in regulating body temperature and synthesizing vitamin D when exposed to sunlight. Choices A, B, and C are incorrect. The liver is the largest internal organ, the brain is the control center of the body, and the heart is a vital organ responsible for pumping blood throughout the body. However, none of these organs are the largest in terms of surface area or overall size.

Correct Answer: B

Rationale: The correct term for a microorganism that lives on or in the human body without causing harm is a commensal microorganism. Commensal microorganisms coexist with the host without causing disease or harm. Choice A, 'Bacteria,' is too broad as not all bacteria are harmless in the body. Choice C, 'Microorganism,' is a general term and does not specifically refer to the harmless nature of the organism. Choice D, 'Host,' refers to the organism harboring the microorganism, not the microorganism itself.

Correct Answer: B

Rationale: The correct answer is B: Ball-and-socket joint. A ball-and-socket joint, like the ones found at the shoulder and hip, allows for a wide range of motion. These joints provide multidirectional movement due to the rounded end of one bone fitting into the cup-like socket of another bone, enabling flexion, extension, abduction, adduction, and rotation. Choice A, Hinge joint, is incorrect because hinge joints allow movement in one plane, like a door hinge, and do not provide the wide range of motion seen at the shoulder and hip. Choice C, Pivot joint, is incorrect because pivot joints allow rotation around a single axis, such as the neck, and do not provide the same range of motion as ball-and-socket joints. Choice D, Saddle joint, is incorrect as saddle joints allow movement in multiple directions but are not as versatile or allow as wide a range of motion as ball-and-socket joints.

Correct Answer: D

Rationale: The correct answer is D, 'Scientific Theory.' A scientific theory is a well-substantiated explanation of an aspect of the natural world. It is based on a large body of evidence and has withstood rigorous testing and scrutiny. Scientific theories are considered the strongest scientific arguments because they have predictive power and are supported by a significant amount of empirical data. Choice A, 'Scientific Hypothesis,' is a proposed explanation for a phenomenon but lacks the extensive evidence and testing that theories undergo. Choice B, 'Scientific Law,' describes a consistent and predictable relationship between variables but does not explain why the relationship exists. Choice C, 'Scientific Study Conclusion,' may be based on a single study and lacks the comprehensive nature and validation that theories possess.

Correct Answer: C

Rationale: The correct answer is C: Renal vessel damage. High blood pressure can lead to damage in blood vessels throughout the body, including the kidneys. When blood vessels in the kidneys are affected, it can impair kidney function and potentially lead to kidney disease. Smoking (Choice A) and excessive dietary salt (Choice B) can contribute to high blood pressure but are not direct effects of high blood pressure itself. Older age (Choice D) is a risk factor for developing high blood pressure but is not a direct effect of high blood pressure.

Correct Answer: B

Rationale: The correct answer is B. Alleles are different forms of a gene that can exist at a specific locus. They represent variations of a gene and are inheritable. Choice A is incorrect as it does not fully capture the concept of an allele, which is a specific form of a gene rather than a substitution. Choice C is incorrect as alleles are not a grouping of various genes but rather different forms of a single gene at a specific locus. Choice D is also incorrect as it does not accurately describe alleles; alleles are variations of genes, not base pairs.