A smelt is a type of small fish. Smelt lengths have a standard deviation of 2 cm. A simple random sample of 30 smelts has a sample mean length of 7.5 cm.

The null hypothesis is H 0 : mu=8.5 cn against : u < 8.5 cm, where u is the mean length of all smelts. What can be concluded from the test ? Use alpha=0.01 .
A reject the null hypothesis

B cannot do test without knowing the value of u

C need to use a larger value of a

D accept the null hypothesis