#### Answer

B

#### Work Step by Step

$ 9\times 9 = 81$
$ 10\times 10 = 100$
We know that the square root of 81 is 9, and the square root of 100 is 10. Because the square root of 85 is between the square root of 81 and the square root of 100, we can conclude that $ \sqrt {85}$ is between 9 and 10.