Answer:
C;

Explanation:
To find the missing length of a right triangle, we can use the Pythagorean Theorem. This theorem states that
, where a and b are the legs of a right triangle and c is the hypotenuse. In our problem, we are solving for one of the legs. In this problem we'll say that a=8 and b=x while c=9. Now, let's solve for x.

a=8
b=x
c=9

So, our answer must be C.
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