Just wanted to pop in and do a really quick summary since nothing has been posted yet.
Violates right of businesses to determine their own policies and rules
→
Legislation to designate sections for smokers/non-smokers cannot be justified
In other words...
Violates → ~Justified; Justified → ~Violates
The first thing we must realize here is basically that this is a sufficient assumption answer question disguised as a principle question. The "enables the conclusion to be properly drawn" shows us this.
(A) This doesn't bridge the gap. It says (J→~H) but we are looking for (J→~V). To "violate" a right and to "harm" a person are not synonymous things.
(B) Contradicts conclusion
(D) Scope...employees?
(E) Contradicts the premise as it says that the "main issue" is finding a compromise while the argument says that the "main issue" is the violation of the rights of businesses. Also, the conclusion is not about compromising, it is about turning down the legislation.
(C) Perfectly bridges the gap. It is saying that the right of businesses > the right of the government. Saying this lets the argument logically follow.
Hope you liked the very quick and dirty explanation.