Which structure in the lungs is the site of gas exchange?

Correct Answer: B

Rationale: The correct answer is B: Alveoli. Alveoli are tiny air sacs in the lungs where gas exchange occurs. Oxygen from inhaled air diffuses into the bloodstream, while carbon dioxide from the blood is released into the alveoli to be exhaled. The trachea (Choice A) is the windpipe that carries air to and from the lungs, but it is not involved in gas exchange. Bronchioles (Choice C) are small air passages within the lungs that branch off from the bronchi, leading air to the alveoli but not directly involved in gas exchange. The diaphragm (Choice D) is a muscle below the lungs that helps in breathing by expanding and contracting the chest cavity, but it is not the site of gas exchange.

Correct Answer: D

Rationale: The correct answer is D. Positive correlation indicates that as one variable increases, the other variable also increases. In this case, when plotting a comparison of rainfall to plant length, if the line trends to the upper right, it shows a positive correlation where as rainfall increases, plant length also increases. Choices A, B, and C show either no correlation or negative correlation, as they describe scenarios where the variables move in different or opposite directions.

Correct Answer: A

Rationale: The primary function of the cardiovascular system is indeed to transport oxygen and nutrients to various tissues in the body. Choice B, 'To regulate blood pressure,' is incorrect as blood pressure regulation is one of the functions of the cardiovascular system but not its primary function. Choice C, 'To digest food,' is incorrect as digestion is primarily a function of the digestive system, not the cardiovascular system. Choice D, 'To filter waste products,' is incorrect as waste product filtration is primarily carried out by the kidneys and liver, not the cardiovascular system.

Correct Answer: B

Rationale: The correct answer is the Laryngopharynx. It is a common passageway for both food and air. The Esophagus (Choice A) is solely for transporting food from the throat to the stomach. The Nasopharynx (Choice C) is primarily involved in the passage of air. The Trachea (Choice D) is responsible for conducting air to and from the lungs and does not play a role in the passage of food.

Correct Answer: B

Rationale: The medulla oblongata is the correct answer because it is responsible for controlling involuntary functions such as breathing and heart rate. The cerebrum (Choice A) is primarily associated with higher brain functions like thinking and voluntary movements, not with regulating basic bodily functions like breathing and heart rate. The thalamus (Choice C) serves as a relay station for sensory information but is not directly involved in controlling breathing and heart rate. The cerebellum (Choice D) plays a role in coordination and balance, not in regulating respiratory and cardiac functions.

Correct Answer: C

Rationale: The correct answer is IgG. IgG is the only antibody that can cross the placenta, providing passive immunity to the developing fetus. IgA, IgD, and IgM do not cross the placenta. IgA is mainly found in mucosal secretions, IgD is involved in the activation of B cells, and IgM is the first antibody produced in response to an infection, but it does not cross the placental barrier.

Correct Answer: B

Rationale: The medulla oblongata is located at the base of the brainstem and is responsible for controlling vital involuntary functions such as breathing, heart rate, and blood pressure. The cerebrum, although the largest part of the brain, is primarily responsible for higher brain functions like thinking and voluntary muscle movements. The cerebellum is involved in coordination, balance, and muscle control. The thalamus acts as a relay station for sensory information but is not directly responsible for regulating involuntary functions like breathing and heart rate. Therefore, the correct answer is the medulla oblongata.

Correct Answer: D

Rationale: The pia mater is the correct answer. It is a thin, innermost layer of the meninges that contains numerous nerves and blood vessels, providing nourishment to the underlying brain cells and spinal cord. The arachnoid mater (Choice A) is the middle layer of the meninges and does not contain as many nerves and blood vessels as the pia mater. The dura mater (Choice B) is the tough, outermost layer of the meninges and is not responsible for supplying nourishment. The periosteum (Choice C) is a connective tissue membrane covering bones, not part of the meninges.

Correct Answer: D

Rationale: The correct answer is D, 'Recessive Inheritance.' Mendelian inheritance involves traits controlled by single genes with dominant and recessive alleles. Incomplete dominance (choice A) is a non-Mendelian inheritance pattern where the heterozygous phenotype is a blend of the two homozygous phenotypes. Polygenic alleles (choice B) involve multiple genes contributing to a single trait, not following Mendelian principles. Combination inheritance (choice C) is not a recognized term in genetics and does not describe Mendelian inheritance patterns.