Correct Answer: A

Rationale: A proper fraction is characterized by having a numerator smaller than the denominator, while an improper fraction has a numerator larger than the denominator. Therefore, choice A is correct. Choice B is incorrect because it states the opposite relationship between the numerator and denominator for proper and improper fractions. Choice C is incorrect as it describes a fraction where the numerator is equal to the denominator, which is a different concept. Choice D is incorrect as it associates a numerator being smaller than the denominator with an improper fraction, which is inaccurate.

Correct Answer: A

Rationale: To correctly order the numbers from least to greatest, we start with the smallest number, which is -271.906, followed by -193.823, 145.884, and finally 235.971. Therefore, the correct order is -271.906, -193.823, 145.884, 235.971. Choice A is correct. Choice B is incorrect as it incorrectly places 235.971 before -193.823. Choice C is incorrect as it starts with the largest number, 145.884. Choice D is incorrect as it starts with -193.823, which is not the smallest number in the list.

Correct Answer: B

Rationale: To find the area of a square, you square the length of one side. In this case, the side length is 3.1m. So, Area = side² = 3.1m 3.1m = 9.61m². Therefore, the correct answer is 9.61m². Choice A (12.4m²) is incorrect as it is the result of multiplying 3.1m by 4 instead of squaring it. Choice C (6.2m²) is incorrect as it is half of the correct answer. Choice D (9.1m²) is incorrect as it is the result of squaring the wrong value (3.1²).

Correct Answer: A

Rationale: Choice A represents no correlation between two variables as it states that as a student's class attendance decreases, the student's overall grade remains the same. This scenario shows no relationship between class attendance and grade. In contrast, choices B, C, and D show clear correlations between the variables mentioned. Choice B indicates a negative correlation between exercise hours and weight gain, choice C indicates a negative correlation between miles driven and gasoline in the tank, and choice D indicates a positive correlation between water intake and plant growth rate, making them all examples of correlated relationships.

Correct Answer: A

Rationale: The phrase 'thrice a number' translates to 3x, and 'twelve less than' means subtracting 12 from it. Therefore, the correct expression is 3x-12. Choice B, '12-3x', represents '12 less than a number thrice,' which is the opposite of the given phrase. Choice C, '3-12x', does not correctly interpret the phrase provided. Choice D, '12x-3', represents 'a number thrice less than twelve,' which is not the same as the original phrase.