The owner of a local nightclub has recently surveyed a random sample of n = 250 customers of the club. She would now like to determine whether or not the mean age of her customers is greater than 30. If so, she plans to alter the entertainment to appeal to an older crowd. If not, no entertainment changes will be made. Suppose she found that the sample mean was 30.45 years and the sample standard deviation was 5 years. If she wants to have a level of significance at 0.01 what conclusion can she make
选项：

A:There is not sufficient evidence that the mean age of her customers is greater than 30.
B:There is sufficient evidence that the mean age of her customers is greater than 30.
C:There is not sufficient evidence that the mean age of her customers is not greater than 30.
D:There is sufficient evidence that the mean age of her customers is not greater than 30.