; and (B) (i) a national of the United States; (ii) an alien lawfully admitted for permanent residence; or (iii) any other alien authorized to work in the United States with no limitation as to the alien’s employer. (18) Zone 1 occupation The term zone 1 occupation means an occupation that requires little or no preparation and is classified as a zone 1 occupation on— (A) the Occupational Information Network Database (O*NET) on the date of the enactment of this section; or (B) such Database or a similar successor database, as designated by the Secretary of Labor, after the date of the enactment of this section. (19) Zone 2 occupation The term zone 2 occupation means an occupation that requires some preparation and is classified as a zone 2 occupation on— (A) the Occupational Information Network Database (O*NET) on the date of the enactment of this section; or (B) such Database or a similar successor database, as designated by the Secretary of Labor, after the date of the enactment of this section. (20) Zone 3 occupation The term zone 3 occupation means an occupation that requires medium preparation and is classified as a zone 3 occupation on— (A) the Occupational Information Network Database (O*NET) on the date of the enactment of this section; or (B) such Database or a similar successor database, as designated by the Secretary of Labor, after the date of the enactment of this section. (b) Admission into the United States An alien is eligible to be admitted as an H–2C nonimmigrant if the alien— (1) has received an offer of employment from a registered employer