In Illinois, a non-conforming use is:

Option A is incorrect because non-conforming uses are not always illegal. In fact, they are legally protected uses that existed before zoning changes. The concept of 'grandfathering' allows these pre-existing uses to continue even when new zoning regulations would prohibit them. While they may face restrictions on expansion or modification, they are not considered illegal simply because they don't conform to current zoning laws.

Non-conforming uses do not require special permits because they were already legal before the zoning change. Special permits are typically needed for new uses that don't conform to current zoning, not for pre-existing non-conforming uses.

Non-conforming uses generally cannot be freely expanded. Most jurisdictions limit expansion of non-conforming uses to prevent them from becoming more non-conforming over time, though they may be allowed to continue in their existing state.