Correct Answer: B

Rationale: To convert centimeters to kilometers, you need to divide by 100,000 since there are 100,000 centimeters in a kilometer. Therefore, 345 cm · 100,000 = 0.00345 km. The correct answer is 0.0345 km, which is obtained by accurately dividing 345 by 100,000. Choices A, C, and D are incorrect because they do not correctly apply the conversion factor and result in inaccurate values for kilometers.

Correct Answer: B

Rationale: To convert 0.2 liters to milliliters, you need to multiply by 1000 because there are 1000 milliliters in 1 liter. Therefore, 0.2 liters x 1000 = 200 ml. Choice A (20 ml) is incorrect because it represents 0.02 liters, not 0.2 liters. Choice C (2 ml) is incorrect as it represents 0.002 liters. Choice D (2000 ml) is incorrect as it represents 2 liters, not 0.2 liters.

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.'

Correct Answer: D

Rationale: The correct answer is D: Exact Equivalent. The expression 1 inch = 2.54 cm is a direct and precise conversion between inches and centimeters, making it an exact equivalent. It is not related to the Law of Conservation of Units (A) as this principle pertains to the conservation of physical quantities in a system. The International Yard (B) is a unit of measurement, but it is not the term for the given expression. Similarly, while the conversion factor in the expression is standard, it is specifically an exact equivalent and not just a general standard conversion factor (C). Therefore, D is the most appropriate term to describe this specific conversion relationship.

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.