A sample of 25 seniors from a large urban school district has a mean Verbal SAT score of 450. Assume we know that the standard deviation of the population of verbal SAT scores for seniors in the district is S=100. A 90% confidence interval for the mean score u for the population of seniors is used. Which of the following will produce a confidence interval with a smaller margin of error?

A. Using a confidence interval of 95%.

B. Using a sample of 100.

C. Using an upper critical value of 99%.

D. Using a sample of 15 seniors.

E. Using any sample size smaller than 25.