Hello Pa, No, they don't have to be both nouns. They can be noun+noun, noun+adjective, noun+ preposition, noun+verb; adjective+adjective, adjective+preposition, adjective+noun, adjective+verb ; preposition+adjective, preposition+noun, preposition+ verb, preposition+preposition; verb+adjective, verb+ noun, verb+ preposition and verb+ verb .
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