B. Yes, we are 99% confident that the population mean is within the interval.
C. Yes, 225 is below the interval minimum, so it is reasonable to conclude the average cholesterol level is greater than 225 mg/dl.
D. No. Increasing the sample size would decrease the margin of error, so the ends of the interval would move closer to the sample mean of 251.9. So the interval minimum would still be higher than 225.
