The first choice would be usable since sin uses opposite side over hypotenuse.
The second choice would not be useable because the hypotenuse is 9 and therefore cannot be the numerator in the fraction for sin.
The third choice can immediately become eliminated as tan does not involve using the hypotenuse.
The fourth choice would be incorrect since 9 or AB is not included in the choice, therefore it does not solve for the unknown lengths.
The fifth choice is usable because you can go on the other side of the triangle to use as 45°. BC would be the adjacent side and would be over the hypotenuse (9).