C) The suitcase to pack is under the bed. An infinitive phrase will begin with "to" + simple form of the verb. Ex: to smash a spider.
The sentence that contains an infinitive is option C: 'The suitcase to pack is under the bed.' In this example, 'to pack' is the infinitive phrase. Infinitives typically begin with 'to' followed by the base form of a verb, and in this case, it describes the suitcase.
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