Here's why:
* Simple subject: The main noun or pronoun that performs the action of the verb.
* Sentence: Although the sentence is incomplete, it implies an action (e.g., "One week of rehearsals is enough").
* Subject: The subject is the thing that is being talked about, which is "one week of rehearsals".
* Simple Subject: The core part of the subject is the noun "week."
Even though the sentence is incomplete, we can still identify the simple subject by understanding the implied action and finding the main noun that is performing that action.