Correct Answer: D

Rationale: The correct answer is D: 1,000 µg.
To convert milligrams to micrograms, you need to multiply by 1,000 because there are 1,000 micrograms in 1 milligram.

Choices A, B, and C are incorrect because they do not correctly convert milligrams to micrograms. 1 milligram is equal to 1,000 micrograms, making choice D the right answer.

Correct Answer: A

Rationale:
To convert liters to milliliters, you multiply the number of liters by 1000.
Therefore, 0.5 liters equals 500 milliliters. This conversion is standard in various fields, making choice A the correct answer.

Choices B, C, and D are incorrect because they do not correctly convert liters to milliliters.

Correct Answer: A

Rationale:
To convert grams to kilograms, divide by 1,000 since there are 1,000 grams in a kilogram.
Therefore, 34.5 grams · 1,000 = 0.0345 kilograms. The correct answer is 3.45 kg (not 3.45 grams, which is the amount given in the initial question).

Choices B and C are incorrect as they do not involve the conversion from grams to kilograms.
Choice D is also incorrect as it presents the value in grams instead of kilograms.

Correct Answer: B

Rationale:
To convert milliliters to liters, you need to divide by 1000 since there are 1000 milliliters in a liter.
Therefore, 250 milliliters is equal to 250/1000 = 0.25 liters.
Choice A, 25 liters, is incorrect as it is a magnitude higher than the correct answer.
Choice C, 2.5 liters, is also incorrect as it is 10 times greater than the correct conversion.
Choice D, 0.025 liters, is incorrect as it is a magnitude lower than the correct conversion.

Correct Answer: B

Rationale:
To convert 0.1 liter to milliliters, you need to multiply by 1000 because there are 1000 milliliters in a liter.
Therefore, 0.1 liter converts to 100 milliliters.
Choice A (10 ml) is incorrect as it represents 0.01 liters, not 0.1 liters.
Choice C (1000 ml) is incorrect as it represents 1 liter, not 0.1 liters.
Choice D (1 ml) is incorrect as it is too small a quantity for 0.1 liters.