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Option D. We are 95% confident that the mean amount spent on electric service among the 160 households is between $151 and $216.

Explanation:

A confidence interval is a range of values, derived from the sample statistics, which may include the value of an unknown population parameter.

A 95% confidence interval indicates that between 152 of 160 samples (95%) of the same population will produce confidence intervals that will contain the population parameter.

It also means that we have a 95% confidence that the average (average amount) is among the resulting amounts obtained.

Logically, option "D" is missing the final part. This would be: D. We are 95% confident that the mean amount spent on electric service among the 160 households is between $ 15.

This is the only true option, since the test is based on a sample of only 160 households, the entire population of households cannot be included.

Hence, the correct option is:

Option D. We are 95% confident that the mean amount spent on electric service among the 160 households is between $151 and $216.