please help me answer the question

A random sample of 82 college students were asked how many hours do they exercise in a typical week. The data was entered in the Statistix software and the descriptive statistics printouts is shown below:

Descriptive Statistics

Exercise N           82 Lo 93% CI     6.0925 Mean        6.9878 Up 93% CI     7.8831 SD         4.4152 Minimum      0.0000 Median      6.5000 Maximum     22.000 

Suppose it is desired to reduce the width of the confidence interval to get more accurate information. Which of the following will accomplish this goal?

a. Decrease the reliability level

b. Decrease the sample size

c. Decrease the alpha used

d. All of these would result in a narrower interval