Minute Maid states that a bottle of juice contains 473 mL. Consumer groups are interested in determining if the bottles contain less than the amount stated on the label. To test their claim, they sample 30 bottles. The sample mean was 472mL and the standard deviation is 0.2.

What does mu represent here?
A. The average contents of all bottles of juice in the sample, which is unknown.
B. The average contents of all bottles of juice in the population, which is unknown.
C. The average contents of all bottles of juice in the population, which is 472mL.
D. The average contents of all bottles of juice in the sample, which is 472mL.