. For which set of data is the mean 8.1?
6.6, 7.5, 8.1, 9.2, 9.8
8.1, 8.1, 8.7, 8.8, 9.9
4.2, 6.7, 8.1, 5.5, 9.1
8.5, 8.0, 8.0, 9.0, 7.0
6.6, 7.5, 8.1, 9.2, 9.8
8.1, 8.1, 8.7, 8.8, 9.9
4.2, 6.7, 8.1, 5.5, 9.1
8.5, 8.0, 8.0, 9.0, 7.0