What act allowed congress to grant most favored nation status to u. s trading partners?

Where are the following

They are formed to perform a single function or a set of related functions. special district governments are independent, special purpose governmental units, other than school district governments, that exist as separate entities with substantial administrative and fiscal independence from general purpose local governments.most perform a single function, but in some instances, their enabling legislation allows them to provide several, usually related, types of services.  such basic social needs as hospitals and fire protection, to the less conspicuous tasks of mosquito abatement and upkeep of cemeteries.hope this !

Idont know i just posting 4 points