The time to repair an electronic device is a normally distributed random variable measured in hours.For 16 such devices, the average repair time was found to be 240 hours with a standard deviation of 4 hours.A 95% confidence interval is to be constructed on the true average time to repair all electronic devices of this type.Which distribution are you going to use when constructing this confidence interval?

A.	t distribution
B.	z distribution (standard normal distribution)
C.	d distribution
D.	x distribution