What is the main function of the epiglottis, a small flap of cartilage located above the larynx?

Correct Answer: B

Rationale: The main function of the epiglottis is to control the passage of food and air. It acts as a cover for the trachea during swallowing to prevent food from entering the airway. This mechanism ensures that food safely travels down the esophagus to the stomach, while air simultaneously enters the trachea and moves into the lungs for respiration. Choice A is incorrect as the warming and humidifying of inhaled air primarily occur in the nasal cavity. Choice C is incorrect because sound production for speech involves structures like the vocal cords rather than the epiglottis. Choice D is incorrect as sensing foreign objects is not a primary function of the epiglottis; instead, this role is typically associated with sensory receptors in the respiratory tract.

Correct Answer: A

Rationale: Isotopes of the same element are chemically similar because they have the same number of protons. The number of protons in an atom determines its atomic number, which is the defining characteristic of an element. Since chemical reactions primarily involve interactions between the electrons of atoms, having the same number of protons means the atoms have the same basic chemical properties. While isotopes may differ in the number of neutrons, it is the number of protons that dictates the element's identity and chemical behavior. Therefore, choice A is correct because the number of protons directly influences an element's chemical properties, making isotopes of the same element chemically similar despite potentially having different numbers of neutrons. Choices B, C, and D are incorrect because isotopes of the same element can have different numbers of electrons, their chemical properties are not identical due to potential differences in neutron numbers, and although they may have similarities in electron configurations, it is the number of protons that is the key factor determining chemical behavior.

Correct Answer: B

Rationale: A redox reaction involves the transfer of electrons between reactants. In option B, Zn loses electrons to form Zn2+ while H+ gains electrons to form H2. This exchange of electrons demonstrates a redox reaction, making choice B the correct answer. In options A, C, and D, there is no clear transfer of electrons between the reactants, indicating that they are not redox reactions. Option A represents a synthesis reaction, option C represents a decomposition reaction, and option D represents a combustion reaction. These types of reactions do not involve the transfer of electrons between reactants, unlike a redox reaction.

Correct Answer: A

Rationale: In physics, power is defined as the rate at which work is done, which refers to the amount of energy transferred or converted per unit time. Choice B, 'The amount of force applied,' is incorrect as power is related to work done, not just force. Choice C, 'The distance an object travels,' is not the definition of power but rather relates to displacement or distance. Choice D, 'The potential energy of an object,' is not the correct definition of power; potential energy is different from power. Therefore, the correct definition of power in physics is the rate at which work is done.

Correct Answer: B

Rationale: A goiter is a condition characterized by the abnormal enlargement of the thyroid gland. This enlargement can be caused by various factors such as iodine deficiency, thyroid nodules, inflammation, or other thyroid disorders. It is not associated with the overproduction of cortisol (Choice A), underproduction of parathyroid hormone (Choice C), or deficiency of growth hormone (Choice D). Therefore, the correct answer is B, excessive growth of the thyroid gland.

Correct Answer: B

Rationale: The correct answer is B: 206. The adult human skeleton consists of 206 bones. These bones are categorized into the axial skeleton, which includes the skull, vertebral column, and rib cage, and the appendicular skeleton, comprising the bones of the limbs and girdles. Each bone has a specific function in providing structure and support to the body. Choices A, C, and D are incorrect because they do not represent the accurate number of bones in the adult human skeleton. It is essential to remember the correct number of bones in the human skeleton for a better understanding of the skeletal system.

Correct Answer: D

Rationale: Vacuoles in plant cells primarily function as storage organelles. They store water, enzymes, pigments, and waste products, helping to maintain turgor pressure within the cell. This turgor pressure provides structural support for the plant cell. While vacuoles can also participate in transporting substances within the cell, their main role is storage. The synthesis of proteins and lipids is mainly handled by other organelles such as the endoplasmic reticulum and Golgi apparatus. Choice A is incorrect because while vacuoles indirectly contribute to structural support by maintaining turgor pressure, their primary function is storage. Choice B is incorrect as vacuoles are not primarily responsible for transporting substances in and out of the cell. Choice C is incorrect as vacuoles do not synthesize proteins and lipids; this function is carried out by other organelles.

Correct Answer: A

Rationale: Phagocytes are a type of white blood cell that plays a crucial role in the immune system by engulfing and digesting foreign invaders such as bacteria, viruses, and other harmful substances. They are part of the body's innate immune response and are essential for protecting the body against infections. Lymphocytes, on the other hand, are another type of white blood cell involved in the adaptive immune response, producing antibodies, and coordinating immune responses. Platelets are cell fragments involved in blood clotting, while red blood cells are responsible for carrying oxygen to tissues. Therefore, the correct answer is Phagocytes (Choice A) because they are specifically tasked with attacking and destroying foreign invaders in the body, distinguishing them from the other choices which have different functions within the immune system.

Correct Answer: B

Rationale: A) Trait: A trait is a characteristic or feature of an organism that is determined by its genes. B) Mutation: A mutation is a permanent alteration in the DNA sequence that can result from errors during DNA replication, exposure to mutagens, or other factors. C) Allele: An allele is a variant form of a gene that can result in different traits or characteristics. D) Variation: Variation refers to the differences in traits or characteristics among individuals of the same species, which can be influenced by genetic and environmental factors. In this context, the term that specifically refers to a permanent alteration in the DNA sequence is "mutation."