Correct Answer: D

Rationale: To determine the significant figures in the sum of 23.68 and 4.12, we add the numbers which results in 27.8. The sum has 3 significant figures because the least precise number has 2 decimal places. To find the significant figures in the product, we multiply the numbers which equals 97.4096. The product has 4 significant figures since the number with the fewest significant figures has 2 before the decimal point and 4 after. Therefore, the correct answer is D (4 significant figures in the product and 3 in the sum).

Correct Answer: B

Rationale: To find the mass of a 57-mL sample of glycerol, we use the given mass-to-volume ratio. Since 0 mL has a mass of 2 grams, the mass-to-volume ratio is 2g/0mL = 2g/mL. Therefore, for a 57-mL sample, we multiply 2g/mL by 57 mL to get 114 grams, which corresponds to answer choice B. Choice A (8.8 g) is incorrect because it does not align with the calculated mass of 114 g for a 57-mL sample. Choices C (2.9 104 g) and D (72 g) are also incorrect as they are not consistent with the mass-to-volume ratio of 2g/mL provided in the question.

Correct Answer: B

Rationale: Step 1: In measurement, certain digits are the numbers that are known for sure. Step 2: Uncertain digits are the last digit that is estimated or measured. Step 3: We record all the certain digits and one uncertain digit to indicate the precision of the measurement. Step 4: Choice A is incorrect because we do include uncertain digit(s) in the measurement. Step 5: Choice C and D are incorrect as including two or three uncertain digits would provide excessive precision beyond what is known for certain.

Correct Answer: A

Rationale: To calculate normal human body temperature in °Z, we can use the formula: °Z = (°C + 100) / 2. Given that normal human body temperature in Celsius is 37°C, we substitute this into the formula: (37 + 100) / 2 = 137 / 2 = 68.5°Z. Therefore, the correct answer is A: 2968°Z, as it is the closest to 68.5°Z. Summary of other choices: B: 12.4°Z - This is too low, as human body temperature is higher. C: 111°Z - This is too high, as it exceeds the calculated value of 68.5°Z.

Correct Answer: C

Rationale: To convert 4 lb to g, we use the conversion factor provided: 1 lb = 6 g. 1. Multiply 4 lb by 6 g/lb: 4 lb * 6 g/lb = 24 g. 2. Since the question asks for the answer in grams, the correct conversion is 24 g. Therefore, the correct answer is C (7.58 x 10^4 g). Other choices are incorrect because they do not correctly apply the conversion factor or provide the accurate conversion from pounds to grams.