Correct Answer: B

Rationale: To convert from kilometers to meters, you need to multiply by 1,000 since there are 1,000 meters in a kilometer. Therefore, 3 kilometers is equal to 3,000 meters. Choices A, C, and D are incorrect because they do not correctly convert kilometers to meters.

Correct Answer: A

Rationale: The correct answer is A: 298.15 K. The conversion from Celsius to Kelvin is K = C + 273.15. Therefore, 25°C is equivalent to 298.15 K, as 25 + 273.15 = 298.15. Choice B, 273.15 K, is the freezing point of water in Kelvin, not the equivalent of 25°C. Choice C, 250 K, and Choice D, 25 K, are incorrect conversions and do not align with the correct formula for converting Celsius to Kelvin.

Correct Answer: B

Rationale: To convert kilograms to grams, you need to multiply by 1000 since there are 1000 grams in 1 kilogram. Therefore, 0.5 kilograms is equal to 500 grams (0.5 x 1000 = 500). Choice A (50 grams) is incorrect as it is the result of multiplying by 10 instead of 1000. Choice C (5,000 grams) is incorrect as it is the result of adding an extra zero. Choice D (0.5 grams) is incorrect as it represents the original amount in grams, not the converted amount.

Correct Answer: A

Rationale: The metric prefix 'centi-' signifies 10^-2, denoting one-hundredth of a unit. For instance, 1 centimeter equals 0.01 of the base unit. Choice B, 'milli,' represents 10^-3, 'nano' in Choice C represents 10^-9, and 'deci' in Choice D stands for 10^-1. Therefore, the correct answer is 'centi.'

Correct Answer: A

Rationale: To convert liters to milliliters, you need to multiply by 1000 since 1 liter is equal to 1000 milliliters. Therefore, 0.5 liters multiplied by 1000 equals 500 milliliters. Choice A, 500 mL, is the correct answer. Choice B, 50 mL, is incorrect as it represents converting 0.05 liters to milliliters. Choice C, 5 mL, is incorrect as it represents converting 0.005 liters to milliliters. Choice D, 0.5 mL, is incorrect as it represents the original amount in milliliters, not the conversion of liters to milliliters.