Correct Answer: B

Rationale: Estuaries are coastal areas where freshwater from rivers and streams mixes with saltwater from the ocean. They serve as important habitats for a variety of marine life, including fish, birds, and other wildlife. Estuaries provide shelter, breeding grounds, and food sources for many species, making them crucial for the overall health of marine ecosystems. While estuaries can help filter pollutants to some extent, their primary function is to support and sustain diverse populations of plants and animals. Storing carbon dioxide and generating wind power are not main functions of estuaries.

Correct Answer: C

Rationale: Muscle contraction is the correct answer. It is the process by which muscles convert chemical energy (ATP) into mechanical energy (movement). During muscle contraction, the sliding filament theory explains how actin and myosin filaments slide past each other, causing muscle fibers to shorten and generate force. Photosynthesis (option A) is the process by which plants convert light energy into chemical energy. Cellular respiration (option B) is the process by which cells generate ATP from glucose and oxygen. The sliding filament theory (option D) is a detailed explanation of the molecular events that occur during muscle contraction but is not the overall process of converting energy into movement; it focuses on the mechanism within the process of muscle contraction.

Correct Answer: C

Rationale: Amphiprotic substances are those that can both donate and accept protons. They possess characteristics of both acids and bases, making them capable of acting as proton donors and proton acceptors. Choices A and B represent substances that are specific to either donating or accepting protons. Choice D does not describe a substance's ability to donate or accept protons since neutrality does not inherently involve proton donation or acceptance.

Correct Answer: B

Rationale: The recommended daily fluid intake for adults is typically around 2 liters, which is equivalent to about 8 cups or half a gallon. This amount can vary depending on factors such as age, gender, weight, activity level, and climate. Staying adequately hydrated is essential for overall health and helps maintain proper bodily functions, such as regulating body temperature, aiding digestion, and transporting nutrients and oxygen throughout the body. Drinking enough fluids also helps prevent dehydration, which can lead to symptoms like fatigue, headaches, and dizziness. Choice A, 1 liter, is insufficient and may not meet the body's hydration needs, while choices C and D, 3 liters and 4 liters, respectively, are excessive for most adults and could potentially lead to overhydration, which may have negative health consequences. It's important to note that individual fluid needs may vary, so it's always best to consult with a healthcare provider for personalized recommendations.

Correct Answer: B

Rationale: Immunosuppressive drugs work by suppressing the immune system's activity, which can increase the risk of infections as the body's ability to fight off pathogens is compromised. While allergies can be a side effect of some medications, the primary concern with immunosuppressive drugs is the increased susceptibility to infections. Therefore, the correct answer is B, increased susceptibility to infections. Choice A, 'Increased risk of developing allergies,' is incorrect as the primary risk associated with immunosuppressive drugs is not related to allergies. Choice C, 'Both A and B,' is incorrect as the main concern is the increased susceptibility to infections rather than developing allergies. Choice D, 'Neither A nor B,' is incorrect as there is a known risk of increased susceptibility to infections when using immunosuppressive drugs.