Correct Answer: A

Rationale: To convert milligrams (mg) to micrograms (mcg), you need to multiply by 1000 because there are 1000 micrograms in 1 milligram. Therefore, 0.2 mg * 1000 = 200 mcg. This is the correct conversion. Choice B (20 mcg) is incorrect because it does not account for multiplying by 1000. Choice C (2000 mcg) is incorrect as it mistakenly multiplies by 10 instead of 1000. Choice D (2 mcg) is incorrect as it does not involve any conversion from milligrams to micrograms.

Correct Answer: B

Rationale: The metric system is based on powers of 10. This means that units within the system are related by factors of 10, making conversions straightforward by simply shifting the decimal point. The system's simplicity and consistency are derived from this fundamental concept. Choices A, C, and D are incorrect because the metric system's foundation lies in the consistent relationship between units through powers of 10, not through basic arithmetic operations like multiplication, addition, or subtraction.

Correct Answer: B

Rationale: To convert milliliters to liters, you need to divide by 1,000 since there are 1,000 milliliters in a liter. Therefore, 3,450 mL · 1,000 = 3.45 liters. Choice A (0.345 liters) is incorrect as it incorrectly moves the decimal point. Choice C (34.5 liters) is incorrect as it overestimates the conversion. Choice D (345 liters) is incorrect as it overestimates by an order of magnitude.

Correct Answer: B

Rationale: The correct answer is B: 1000 meters. One kilometer is equivalent to 1000 meters. Therefore, 1000 meters is the accurate conversion from kilometers to meters. Choices A, C, and D are incorrect. Choice A (100 meters) is incorrect as it represents 1/10th of a kilometer. Choice C (500 meters) is incorrect as it is half the value of a kilometer. Choice D (2000 meters) is incorrect as it exceeds the value of a kilometer.

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.