To my mind, learning is empowering in that it gives you a clearer sense of knowing what you know and knowing what you don't know (and this is empowering in that it helps make more pertinent questions, have sharper insight, and more precise understanding).
Light and darkness are two opposite things being contradicted in this sentence; this is antithesis.
You're answer is option A "effect." Remember that effect means to change due to a result, and affect means to have a effect on something.
Hope this helps!
The FBI followed them for 4 months
