Answer: A): 15.90 ounces to 16.4 ounces.
Explanation:
Considering the standard deviation is 0.25 ounces. The mean of the juice is 16.15 ounces. Additionally, 68% is one standard deviation away from the mean.
With that being said, you would do the following calculations:

This question relates to The Empirical Rule and understanding how it works. A brief summary is that within one standard deviation of the mean, that is where 68% of the data lies. Two standards deviations is 95%. And three standard deviations is 99.5%.
The formula:
the mean PLUS OR MINUS the standard deviation.