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.

Correct Answer: B

Rationale: The prefix 'centi' means 0.01, which is one-hundredth of the base unit. For example, 1 centimeter is equal to 0.01 meters. Choice A (0.1) is incorrect as it represents 'deci,' which means one-tenth. Choice C (0.001) is incorrect as it represents 'milli,' which means one-thousandth. Choice D (1) is incorrect as it is not a valid interpretation of the prefix 'centi.' Therefore, the correct answer is B.

Correct Answer: C

Rationale: The correct answer is C: 0.13 inches. When converting decimals to inches, the value remains the same. Choice A, 0.013 inches, represents a smaller value than 0.13 inches as it has an extra zero. Choice B, 1.3 inches, is incorrect as it is a larger value than 0.13 inches. Choice D, 13 inches, is significantly larger than 0.13 inches, making it an incorrect conversion.

Correct Answer: A

Rationale: To find the product of 0.5 and 20, you multiply them together. 0.5 x 20 = 10. This calculation involves multiplying a decimal (0.5) by a whole number (20). Choice A, '10', is the correct answer. Choice B, '15', is incorrect as it does not accurately represent the result of multiplying 0.5 by 20. Choices C and D, '20' and '25', are also incorrect as they do not reflect the correct calculation. This question assesses your ability to perform basic arithmetic operations involving decimals and whole numbers.

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'.