6. A researcher wants to construct a 95% confidence interval for the average lifespan for a species of fly. She planned to use a sample of 50 of the flies. However, she wants an interval that has a smaller margin of error. Which of the following will necessarily result in a reduced interval width?
A. Decrease the sample size and decrease the confidence level.
B. Decrease the sample size and increase the confidence level.
C. Decrease the confidence level.
D. Increase the confidence level.