“Domestic interested party”, when used in this part, means:

(a) A manufacturer, producer, or wholesaler in the United States of a like product,

(b) A certified union or recognized union or group of workers which is representative of an industry engaged in the manufacture, production, or wholesale in the United States of a like product, or

(c) A trade or business association a majority of whose members manufacture, produce, or wholesale a like product in the United States.