Convert 0.5 centimeters to millimeters.

Correct Answer: A

Rationale: To convert centimeters to millimeters, you need to multiply by 10 since 1 centimeter equals 10 millimeters. Therefore, 0.5 centimeters is equal to 5 millimeters (0.5 * 10 = 5). Choice A, '5 mm,' is the correct answer. Choice B, '0.5 mm,' is incorrect as it would be equivalent to half a millimeter. Choice C, '50 mm,' is incorrect as it represents 50 millimeters, which would be the equivalent of 5 centimeters. Choice D, '0.05 mm,' is incorrect as it represents 0.05 millimeters, which is a fraction of 1 millimeter.

Correct Answer: B

Rationale: The base unit for mass in the metric system is grams. Grams are the fundamental unit of mass in the metric system, representing smaller quantities than kilograms and tons. Milligrams are a smaller unit of mass, kilograms are a larger unit, and tons are even larger units. Therefore, the correct choice is grams.

Correct Answer: D

Rationale: To convert milligrams to micrograms, you need to multiply by 1000, not 10000. Therefore, to convert 0.075 mg to mcg, you multiply 0.075 by 1000, giving you 75 mcg. The correct answer is not provided in the choices, and the correct conversion is 75 mcg, which is not listed as an option. Choices A, B, and C are incorrect because they do not reflect the correct conversion factor. Choice D, 750 mcg, is a common mistake made by incorrectly adding a zero. It is important to remember that the conversion from milligrams to micrograms involves multiplying by 1000, not adding extra zeros.

Correct Answer: B

Rationale: The decimal 0.2 is already at the nearest tenth, so it does not need to be rounded. Rounding to the nearest tenth means keeping one decimal place, which is already the case with 0.2. Therefore, the correct answer is 0.2, as it is already at the specified rounding point. Choices A, C, and D are incorrect because they represent values that are not the result of rounding 0.2 to the nearest tenth. 0.1 is rounding down, 0.3 is rounding up, and 0.25 is not the nearest tenth of 0.2.

Correct Answer: C

Rationale: To express 0.4 in inches, you don't need to convert it further as it is already in inches. Therefore, the correct answer is 0.4 inches. Choice A (0.04 inches) is incorrect as it represents a smaller quantity. Choice B (4 inches) and Choice D (40 inches) are incorrect as they represent larger quantities, which are not equivalent to 0.4 inches.

Correct Answer: B

Rationale: To convert liters to milliliters, you need to multiply by 1,000 since there are 1,000 milliliters in a liter. Therefore, 1.5 liters x 1,000 = 1,500 milliliters. Choice A, 15 mL, is incorrect as it represents the conversion of 0.015 liters. Choice C, 150 mL, is incorrect as it represents the conversion of 0.15 liters. Choice D, 150,000 mL, is incorrect as it represents the conversion of 150 liters.

Correct Answer: A

Rationale: To convert milligrams to micrograms, you need to multiply by 1000, not 10000. Therefore, 0.025 mg is equal to 25 mcg. The correct conversion is obtained by recognizing that 1 milligram (mg) is equal to 1000 micrograms (mcg). Choices B, C, and D are incorrect because they do not correctly convert milligrams to micrograms. Choice B is 10 times the correct answer, choice C is 100 times less, and choice D is 100 times less than the correct conversion.

Correct Answer: A

Rationale: To convert 0.004 to a ratio, we can express it as 4/1000, which simplifies to 1/250. Therefore, the correct ratio is 1:250. Choice B (4:200) is incorrect as it simplifies to 1:50, not 1:250. Choice C (2:400) simplifies to 1:200, which is also incorrect. Choice D (9:200) simplifies to a ratio greater than 1:1, which is not equivalent to 1:250.

Correct Answer: A

Rationale: The correct answer is 'meter.' In the metric system, 'm' stands for meter, which is the base unit for length. Choice B, 'mole,' is a unit used in chemistry to represent an amount of substance. Choice C, 'milli,' represents a prefix indicating one-thousandth, and choice D, 'micro,' represents a prefix indicating one-millionth. Therefore, the correct choice is 'A: meter.'