Which of the following hormones is produced by the adrenal medulla and prepares the body for a stressful situation?

Correct Answer: C

Rationale: The correct answer is C: Epinephrine (adrenaline). Epinephrine is produced by the adrenal medulla and is responsible for preparing the body for a stressful situation. It increases heart rate, dilates airways, and mobilizes energy stores to help the body respond to a fight-or-flight scenario. Testosterone (Choice A) is a sex hormone produced by the testes in males and in smaller amounts by the ovaries in females, not by the adrenal medulla. Cortisol (Choice B) is a stress hormone produced by the adrenal cortex, not the adrenal medulla. Growth hormone (Choice D) is produced by the pituitary gland and is involved in growth, metabolism, and various bodily functions, not by the adrenal medulla.

Correct Answer: C

Rationale: Reactivity refers to a substance's ability to undergo a change that transforms it into a different substance through a chemical reaction. In this context, reactivity specifically refers to the chemical behavior of a substance. Density, mass, and volume are physical properties of a substance and do not describe its ability to undergo a chemical change. Density is the mass per unit volume, mass is the amount of matter in an object, and volume is the amount of space occupied by an object. Therefore, reactivity is the most appropriate term to describe a substance's ability to undergo a transformation into a different substance.

Correct Answer: A

Rationale: The period of a wave is defined as the time it takes for one complete wave cycle to pass a point. It is a crucial parameter in wave analysis and is typically measured in seconds. The period is directly related to the frequency of the wave, as they are reciprocals of each other. Therefore, the correct answer is the time it takes for one complete wave cycle to pass a point (choice A). The period is not related to the number of waves passing a point per unit time (choice C), the distance between two adjacent crests or troughs (choice B), or the maximum displacement of particles in a medium due to the wave (choice D).

Correct Answer: A

Rationale: In biological classification, a phylum is a higher taxonomic rank than a class. A phylum is a broader category that encompasses multiple classes within it. It represents a group of organisms sharing a common body plan or evolutionary history. On the other hand, a class is a more specific category within a phylum that includes organisms with similar characteristics. Therefore, phyla are broader and more general compared to classes. Choice B is incorrect because classes are more specific categories within phyla. Choice C is incorrect as phyla and classes are distinct hierarchical levels in taxonomy. Choice D is incorrect because phyla and classes are not restricted to specific types of organisms; they can apply to various organisms across the biological kingdom.

Correct Answer: C

Rationale: The magnitude of the frictional force acting on the book sliding across a table is determined by both the mass of the book and the normal force from the table. Frictional force is proportional to the normal force (which is influenced by the weight of the book, i.e., its mass) and is affected by the surfaces in contact and other friction-related factors. Therefore, both the mass of the book and the normal force from the table are essential in determining the frictional force experienced by the book during its sliding motion. Choices A, B, and D are incorrect because friction is a result of the interaction between the surfaces and is influenced by both the mass of the object and the normal force acting on it.

Correct Answer: C

Rationale: A commensal relationship is a type of symbiotic relationship in which one organism benefits, while the other is neither harmed nor benefited. In this case, E. coli living in the gut is an example of a commensal relationship because it can benefit from the environment in the gut without causing harm to the human host. Option A, Salmonella causing food poisoning, is an example of a pathogenic relationship where the microorganism causes harm to the host. Option B, Staphylococcus aureus causing skin infections, is also an example of a pathogenic relationship where the microorganism causes harm to the host. Option D, Rabies virus causing neurological disease, is another example of a pathogenic relationship where the microorganism causes harm to the host.

Correct Answer: C

Rationale: The epiglottis plays a crucial role during swallowing by covering the trachea to prevent food or liquid from entering the airway, which could lead to aspiration. By acting as a lid over the trachea, it ensures that food passes down the esophagus to the stomach, preventing it from entering the lungs. Choice A is incorrect as the swallowing reflex is a coordinated muscular action involving the tongue and throat muscles. Choice B is incorrect as grinding food into smaller pieces is primarily the function of the teeth and the initial stages of digestion. Choice D is incorrect as the storage of saliva for lubrication is not a function of the epiglottis, but rather involves salivary glands.

Correct Answer: C

Rationale: Lymph moves through the lymphatic vessels due to the presence of one-way valves within the vessels. These valves prevent the backflow of lymph and help propel the fluid forward as muscles contract and relax or due to breathing movements. Unlike blood circulation, the lymphatic system does not rely on the pumping action of the heart to move lymph. Choice A is incorrect because lymphatic circulation does not depend on the pumping action of the heart. Choice B is partly correct as muscle contractions and breathing movements do assist in propelling lymph, but the primary mechanism is the presence of one-way valves within the vessels, making choice C the most accurate answer. Choice D is incorrect as not all options listed contribute to how lymph moves through the lymphatic vessels.

Correct Answer: A

Rationale: Tendons, the correct answer, are fibrous connective tissues that connect muscles to bones, enabling movement at joints. They play a crucial role in transmitting the force generated by muscles to the bones, facilitating movement. Ligaments (option B) connect bone to bone, providing stability to joints. Cartilage (option C) is a flexible tissue that acts as a cushion, reducing friction between bones in joints. Bursae (option D) are fluid-filled sacs located near joints that help reduce friction between tissues such as tendons and bones.