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Which structure helps regulate body temperature by constricting or dilating in response to temperature changes?
- A. Sebaceous glands
- B. Hair follicles
- C. Sweat glands
- D. Langerhans cells
Correct Answer: C
Rationale: Sweat glands play a crucial role in regulating body temperature by producing sweat that evaporates from the skin surface. This evaporation cools the body when it is hot and helps to maintain a stable internal temperature. Sebaceous glands produce oil to lubricate the skin, hair follicles are responsible for hair growth, and Langerhans cells are a type of immune cell in the skin. Therefore, the correct answer is 'Sweat glands' as they are specifically designed to respond to temperature changes by constricting or dilating to help regulate body temperature.
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What is the main function of the epiglottis?
- A. To store bile
- B. To absorb nutrients
- C. To prevent food from entering the trachea
- D. To produce digestive enzymes
Correct Answer: C
Rationale: The epiglottis is a flap of cartilage located at the base of the tongue that covers the opening of the trachea during swallowing to prevent food and liquids from entering the airway. This action helps direct food and liquids into the esophagus, which leads to the stomach for digestion, while also protecting the respiratory system from potential blockages that could lead to choking or aspiration pneumonia. Options A, B, and D are incorrect as the epiglottis is not involved in storing bile, absorbing nutrients, or producing digestive enzymes. Understanding the role of the epiglottis in the swallowing process is crucial for maintaining proper respiratory and digestive functions.
Which biome is characterized by cold temperatures, permafrost, and coniferous trees?
- A. Tundra
- B. Desert
- C. Rainforest
- D. Savanna
Correct Answer: A
Rationale: A) Tundra: This biome is characterized by cold temperatures, permafrost (permanently frozen subsoil), and vegetation such as mosses, lichens, and coniferous trees like spruce and fir. The tundra is found in high latitudes near the Arctic Circle and high altitudes in mountainous regions. It is a cold and harsh environment where the ground remains frozen for a significant part of the year. The coniferous trees in this biome are adapted to survive in extreme cold conditions.
B) Desert: Deserts are characterized by low precipitation levels and high temperatures, with sparse vegetation adapted to arid conditions.
C) Rainforest: Rainforests are characterized by high levels of rainfall, warm temperatures, and dense vegetation with a variety of plant and animal species.
D) Savanna: Savannas are tropical grasslands with scattered trees and shrubs, characterized by a distinct wet and dry season. They have a different climate pattern compared to the cold temperatures and permafrost found in the tundra biome.
In this case, the description of cold temperatures, permafrost, and coniferous trees aligns most closely with the characteristics of the tundra biome, making option A the correct answer.
A light ray travels from air (refractive index 1.00) into water (refractive index 1.33). What happens to its speed and direction?
- A. Speed increases, direction bends towards the normal.
- B. Speed increases, direction bends away from the normal.
- C. Speed decreases, direction bends towards the normal.
- D. Speed and direction remain unchanged.
Correct Answer: C
Rationale: When a light ray travels from air (lower refractive index) to water (higher refractive index), its speed decreases due to the change in the medium. This is because light travels slower in denser mediums. As the light ray enters the denser medium, water in this case, it bends towards the normal (the line perpendicular to the surface of the water). This phenomenon is known as refraction. Choice A is incorrect as the speed of light decreases when entering a denser medium. Choice B is incorrect as the direction bends towards the normal, not away from it. Choice D is incorrect as the speed and direction of the light ray do change when moving from air to water.
How does an unbalanced force affect an object at rest?
- A. It maintains the object's state of rest
- B. It does not affect the object's rest
- C. It moves the object into motion
- D. It decreases the object's mass
Correct Answer: C
Rationale: An unbalanced force acting on an object at rest will cause the object to move into motion. This is in accordance with Newton's first law of motion, which states that an object at rest will remain at rest unless acted upon by an external force. Therefore, option C, 'It moves the object into motion,' is the correct answer. Choices A and B are incorrect because an unbalanced force disrupts the object's state of rest. Choice D is incorrect as force does not affect the mass of an object.
In the reaction 4Al + 3O2 → 2Al2O3, what is the mole ratio of aluminum to oxygen?
- A. 4:3
- B. 2:3
- C. 3:2
- D. 3:4
Correct Answer: A
Rationale: The balanced chemical equation shows that 4 moles of aluminum react with 3 moles of oxygen to produce 2 moles of aluminum oxide. Therefore, the mole ratio of aluminum to oxygen is 4:3. Choice B (2:3) is incorrect because it does not reflect the correct ratio based on the balanced equation. Choice C (3:2) and Choice D (3:4) are also incorrect as they do not represent the correct mole ratio of aluminum to oxygen according to the balanced chemical equation.