This is a prediction/evidence evaluation question. Scientist 2 explicitly proposes that dark matter consists of MACHOs: "black holes, neutron stars, brown dwarfs (failed stars), and rogue planets." Finding billions of rogue planets and brown dwarfs would directly confirm Scientist 2's hypothesis. Choice B is correct. Choice A (Scientist 1) proposes WIMPs (exotic particles), not normal matter objects. Choice C (Scientist 3) rejects the existence of missing mass entirely. Choice D is illogical—Scientists 1 and 3 have opposing views. Pro tip: Match new evidence to the specific prediction each hypothesis makes.

This is a scientific reasoning question asking you to explain observed data using biological principles. The Introduction defines endotherms as animals that "generate their own body heat to maintain a constant internal temperature." At cold temperatures (5°C), the mouse must burn more energy (consume more O₂) to maintain its internal temperature against the cold environment. At 25°C (thermoneutral zone), less energy is needed because ambient temperature is closer to body temperature. This explains why metabolic rate is high at 5°C and drops to minimum at 25°C. Choice A correctly explains this thermoregulation principle. Choice B (more active at high temp) contradicts that animals were "kept at rest." Choice C (enzymes more efficient at 5°C) is backwards—enzyme efficiency typically increases with temperature up to an optimal point. Choice D (hibernation) contradicts the high metabolic rate shown. Pro tip: Connect data patterns to biological definitions provided in the introduction.

This is a concept application question requiring you to understand solubility definitions and apply them to graph data. According to Figure 1, KNO₃ has a solubility of approximately 60 g/100 g H₂O at 40°C. This means up to 60 g can dissolve at this temperature. Since the student only dissolved 50 g, which is less than the maximum of 60 g, more could still dissolve. By definition, this makes the solution unsaturated (not yet at maximum capacity). Choice B is correct. Choice A (saturated) would only be true if exactly 60 g were dissolved. Choice C (supersaturated) would require dissolving MORE than the maximum, which typically requires special cooling techniques. Choice D (dilute/insoluble) is nonsensical—the graph clearly shows KNO₃ does dissolve at 40°C. Pro tip: Saturated = at maximum; Unsaturated = below maximum; Supersaturated = above maximum (unstable).

This is a scientific reasoning question requiring both data interpretation and biological knowledge. Figure 1 shows green light produced only 5 bubbles, dramatically lower than clear (45), red (40), and blue (38). This indicates green light is least effective for photosynthesis. The biological explanation is that chlorophyll, the primary photosynthetic pigment, reflects green light (which is why plants appear green to us) rather than absorbing it. Since reflected light isn't absorbed, it can't be used for photosynthesis. Choice C is correct on both parts. Choice A incorrectly identifies blue as lowest (it was 38, not 5). Choice B incorrectly identifies red. Choice D incorrectly identifies clear. Pro tip: Plants appear the color they reflect because they're NOT using that wavelength for photosynthesis.

This is a claim evaluation question requiring you to check whether data support a statement. The claim mentions "sudden change in density at the core-mantle boundary." Looking at 2,900 km: Figure 1 shows P-wave velocity drops sharply from 13 to 8 km/s (sudden change in velocity), and Figure 2 shows density jumps from 5.5 to 10.0 g/cm³ (sudden change in density). These abrupt discontinuities support the claim of sudden material property changes. Choice A is correct. Choice B mentions temperature, which isn't shown in either figure. Choice C is factually wrong—velocity changes dramatically. Choice D is factually wrong—density increases, not decreases. Pro tip: For support questions, verify whether the data actually show what the claim describes.

This is a hypothesis evaluation question. The hypothesis claims "linear" increase means the rate should keep increasing proportionally with concentration. Table 2 shows: 0.0% → 2, 0.5% → 45 (huge jump), 1.0% → 58 (moderate increase), 1.5% → 60 (small increase of 2), 2.0% → 61 (tiny increase of 1). The change from 60 to 61 indicates plateau (leveling off), not linear growth. At this point, adding more CO₂ barely increases photosynthesis—the plant has reached saturation. Choice C correctly identifies this plateau as evidence against the hypothesis. Choice A misses that overall increase doesn't mean LINEAR increase. Choice B focuses on one pair of trials, missing the plateau at the end. Choice D is factually wrong—rate didn't decrease. Pro tip: "Linear" means proportional increases throughout—plateaus contradict linearity.

Exercise raises heart rate according to the before-and-after comparison data. The table would show higher average heart rates after the 30-minute workout compared to pre-exercise measurements. This demonstrates the cardiovascular system's normal response to physical activity, where increased oxygen and nutrient demands require faster circulation. This is a fundamental physiological response to exercise stress.

More sleep correlates with higher cognitive performance scores according to the table data. The results would show increasing cognitive scores as sleep duration increases, demonstrating the positive relationship between adequate rest and mental function. This reflects well-established research on sleep's role in memory consolidation, attention, and cognitive processing. The correlation supports the importance of sufficient sleep for optimal brain performance.

The conclusion is valid if memory scores increase with caffeine doses according to the table data. The results would show higher memory retention scores at increasing caffeine levels, demonstrating caffeine's cognitive enhancement effects. This supports the stimulant's role in improving alertness and memory consolidation processes. If the data show a clear positive relationship between caffeine dose and memory performance, the author's conclusion is justified by the experimental evidence.

Enzyme activity peaks at 37°C based on the experimental data. The table would show enzyme activity levels increasing up to 37°C and then decreasing at higher temperatures, creating an optimal temperature curve. This pattern reflects the typical behavior of enzymes, which have an optimal temperature where their three-dimensional structure allows maximum catalytic activity. Temperatures above the optimum cause denaturation and reduced activity.