Answer:
C
Explanation:
first you need to memorize
SOH CAH TOA
IT means 
Sine =opposite/hipotenuse
Cosine = adjecent/hipotenuse
tangent = opposite/adjecent
in this case, we need to find sine 
so it's SOH
opposite of theta Θ is 15
and it's hipotenuse , we don't know yet. so need to find it by using Pythagorean theorem
 let it be x
x =√ 15²+ 8²
 =√ 225+ 64
 =√289
 = 17
so the answer is 15/17