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: 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: C

Rationale: The prefix 'femto-' stands for 10^-15, making femtometer equal to 10^-15 meters. The incorrect choices are A and B because 'pico-' represents 10^-12 (picometer) and 'nano-' represents 10^-9 (nanometer), respectively. Choice D is also incorrect as 'pico-' is associated with 10^-12, not 10^-15.

Correct Answer: A

Rationale: To convert a decimal to a fraction, you can write the decimal as a fraction with the decimal part as the numerator and a power of 10 as the denominator. In this case, 0.75 can be written as 75/100. Simplifying this fraction by dividing both the numerator and denominator by 25 gives you 3/4. Therefore, the correct answer is A. Choice B (7/10), Choice C (15/20), and Choice D (1/2) are incorrect because they do not represent the correct conversion of 0.75 into a fraction.

Correct Answer: B

Rationale: The correct answer is B: 100 cm. 1 meter is equivalent to 100 centimeters. Choice A (10 cm) is incorrect as it represents the conversion of decimeters to centimeters. Choice C (1,000 cm) is incorrect as it represents the conversion of meters to millimeters. Choice D (10,000 cm) is incorrect as it represents the conversion of meters to centimeters with an extra zero.