Respuesta :

Sin = opposite over hypotenuse

The opposite side of ∠A is BC, or a
The hypotenuse is c (longest length)

a/c is your answer

B. a/c 

hope this helps
B. a/c 
Sin = opposite/hypotenuse
so opposite angle A is a 
hypotenuse  is c ,
so a/c.
voila!