Rewrite the expression as a single trigonometric ratio.

sinθ / (1 - cos²θ)

Since   sin²θ + cos²θ  =  1

--->    sin²θ  =  1 - cos²θ

So:  sinθ / (1 - cos²θ)  =  sinθ / sin²θ  =  1 / sinθ  =  cscθ

Trig is easier if you can remember the Pythagorean Identity in its three forms:

     sin²θ + cos²θ  =  1      sin²θ  =  1 - cos²θ          cos²θ  =  1 - sin²θ    

Also, there are two more that derive from the above:

     1 + tan²θ = sec²θ          1 + cot²θ + csc²θ

I am confused. I am not sure which answer to pick.