Correct Answer: A

Rationale: The correct answer is A: 10,000 grams. There are 1,000 grams in a kilogram. Therefore, to find the number of grams in 10 kilograms, you multiply 10 (kilograms) by 1,000 (grams/kilogram) to get 10,000 grams. Choice B (100 grams) is incorrect as it represents the conversion for 1 kilogram, not 10 kilograms. Choice C (1000 grams) is incorrect as it is equal to 1 kilogram, not 10 kilograms. Choice D (100,000 grams) is incorrect as it represents the conversion for 100 kilograms, not 10 kilograms.

Correct Answer: A

Rationale: The correct subtraction is 12.02 - 9.99 = 2.03. Therefore, the correct answer is A. Choice B, 2.21, is incorrect as it does not result from the given subtraction. Choice C, 3.17, is also incorrect. Choice D, 7.97, is incorrect as well. Thus, A is the only correct answer.

Correct Answer: B

Rationale: To solve for x, first, subtract 2 from both sides of the equation: 4x = 16. Then, divide by 4 to isolate x: x = 4. Choice A, x = 4, is the correct answer as calculated. Choice C, x = 5, is incorrect because the correct value of x is 4, not 5. Choice D, x = 3, is incorrect as well, as the correct value of x is 4, not 3.

Correct Answer: B

Rationale: The correct answer is B: Decimal. The decimal system, also known as the base-10 system, is the standard system for denoting integer and non-integer numbers in the United States and many other countries. In the decimal system, numbers are represented using 10 digits (0-9). Choices A, C, and D are incorrect. Tertiary, Napoleonic, and Binary number systems are not commonly used for general number representation in the United States.

Correct Answer: C

Rationale: To find the total surface area of the rectangular box, calculate the area of each side and sum them up. The areas of the sides are: 2(40x30) + 2(40x25) + 2(30x25) = 2400 + 2000 + 1500 = 5900 sq cm. Convert this to square meters by dividing by 10,000: 5900/10,000 = 0.59 sq m. Since one sheet covers 0.5 sq m, you would need 2 sheets to cover the box fully, which equals 1 sq m. Therefore, the correct answer is 1.2 sq m. Choice A (0.3 sq m) is too small for the dimensions provided. Choice B (0.6 sq m) is incorrect as it doesn't match the calculated surface area. Choice D (1.8 sq m) is too high for the surface area of the box.