Answer A is gramatically correct. You can use prosses of elimination to solve this if you are unsure. Unfortuanately we are prohibits sounds wrong. Unfortuanately we are prohibiting isn't right either because the ing at the end is in progressive tense. You get the point, prosses of elimination is the best way to solve a problem like this.
proofreading and editing are for changing bigger aspects like sentence structure and organisation, you should change your spelling errors as they come up in the first draft
