Answer:
B. 11.5
Step-by-step explanation:
That missing length can be solved via the equation a^2+b^2=c^2, where the hypotenuse is c. We know A and B, which is 7 and 9.
7^2+9^2=130
sqrt 130 is 11.4017543
Here, you kinda have to break the rules of rounding to say that it is B.
There could be a more efficient route for resolving this answer, but this is the method that I was taught.