Correct Answer: A

Rationale: To convert liters to milliliters, you need to multiply by 1000 since there are 1000 milliliters in a liter. Therefore, 0.5 liters is equal to 500 milliliters. Choices B, C, and D are incorrect because they do not reflect the correct conversion from liters to milliliters.

Correct Answer: A

Rationale: To convert liters to milliliters, you multiply the number of liters by 1000. Therefore, 0.5 liters equals 500 milliliters. This conversion is standard in various fields, making choice A the correct answer. Choices B, C, and D are incorrect because they do not correctly convert liters to milliliters.

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: C

Rationale: The correct answer is C: 1,000 grams. The metric system follows a logical conversion where 1 kilogram is equal to 1,000 grams. This conversion is a fundamental concept in understanding units of measurement. Choices A, B, and D are incorrect because they do not accurately reflect the conversion between kilograms and grams. Option A (10 grams) is incorrect as it represents 1/100th of the correct conversion. Option B (100 grams) is also incorrect as it represents 1/10th of the correct conversion. Option D (10,000 grams) is significantly higher than the actual conversion, making it incorrect. Understanding these basic unit conversions is essential for various fields where precise measurements are necessary.

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.