The correct answer is the subject.
The subject of a sentence is a word, phrase, or an entire clause that is showing us who is performing a particular action. In the case above, the noun clause Whether we win or lose acts as the subject of the sentence. You can replace the entire sentence with a single word; for example, the pronoun SHE: She is not important... Therefore, it will be easier for you to determine that it is actually the subject.
