Correct Answer: A

Rationale: To convert 0.04 grams to milligrams, you need to multiply by 1000, not 10000. Therefore, 0.04 grams equals 40 milligrams (0.04g * 1000 = 40mg). Choice B, '4 mg,' is incorrect as it reflects the value as if it was in grams. Choice C, '400 mg,' is incorrect as it incorrectly multiplies by 100 instead of 1000. Choice D, '0.4 mg,' is incorrect as it incorrectly moves the decimal point to the right instead of multiplying by 1000.

Correct Answer: A

Rationale: To convert liters to milliliters, you need to multiply by 1000 since there are 1000 milliliters in 1 liter. So, 0.20 liters x 1000 = 200 milliliters. This makes choice A, '200 ml,' the correct answer. Choices B, C, and D are incorrect because they do not reflect the correct conversion factor from liters to milliliters.

Correct Answer: A

Rationale: The correct answer is A: 'G'. The prefix 'giga' is commonly represented by the letter 'G' and corresponds to a factor of 10^9, which is equivalent to one billion. Choice B, 'm', represents the prefix 'milli', which corresponds to a factor of 10^-3, not 'giga'. Choice C, 'Gg', is incorrect as the prefix 'giga' is represented by a single letter 'G', not 'Gg'. Choice D, 'g', is incorrect as it represents the prefix 'gram' in the International System of Units (SI) and not the prefix 'giga'.

Correct Answer: A

Rationale: To convert milligrams to micrograms, you need to multiply by 1000. Therefore, 0.1 mg is equal to 100 mcg. This conversion is commonly used in medical calculations. Choice B (10 mcg) is incorrect because it would be the conversion from milligrams to micrograms if multiplied by 100, not 10. Choice C (1000 mcg) is incorrect as it would be the conversion from grams to micrograms if multiplied by 1000. Choice D (1 mcg) is incorrect as it represents the original unit without conversion.

Correct Answer: B

Rationale: To convert kilometers to meters, you need to multiply by 1,000 since there are 1,000 meters in a kilometer. Therefore, 345 km multiplied by 1,000 equals 345,000 meters. Choice A is incorrect as it incorrectly places the comma. Choice C is incorrect as it adds an extra zero at the end. Choice D is incorrect as it adds an extra zero at the beginning, resulting in an incorrect conversion.