Answer:
 D. The 95% confidence interval ranges from 42.78 to 47.22 hours.
Step-by-step explanation:
In a sample of 50 households, the mean number of hours spent on social networking sites during the month of January was 45 hours. In a much larger study, the standard deviation was determined to be 8 hours. 
Here,
n = sample size = 50,
μ = mean = 45,
σ = standard deviation = 8,
We know that, confidence interval will be,

For a confidence interval of 95%, we use z = 1.96, putting the values

