Among the given options, the one that is not a part of early Jaina literature is Option 1: Therigatha.

Reasoning:

1. Therigatha: Therigatha is a collection of poems attributed to early Buddhist nuns, also known as theris. It is a significant text in early Buddhist literature, particularly within the Theravada tradition. The Therigatha is not associated with Jaina literature but belongs to the Buddhist canon.

2. Acarangasutra: The Acarangasutra is one of the oldest and most important canonical texts in Jainism. It is considered a part of early Jaina literature and forms a part of the Jain Agamas, the sacred scriptures of the Jains. The Acarangasutra deals with various ethical and behavioral aspects, including the observance of vows and the conduct of monks and nuns.

3. Sutrakritanga: The Sutrakritanga is another significant text in Jainism and is considered one of the earliest Jaina scriptures. It is part of the Jain Agamas and contains teachings and guidelines for monks and nuns. The Sutrakritanga focuses on topics such as morality, conduct, and discipline within the Jain community.

4. Brihatkalpasutra: The Brihatkalpasutra is a Jaina text that provides a detailed account of rituals, ceremonies, and rules to be followed by Jain monks and nuns. It is considered a part of early Jaina literature and is an essential source for understanding Jaina rituals and practices.

In summary, the Therigatha (Option 1) is not a part of early Jaina literature but belongs to early Buddhist literature, while the Acarangasutra (Option 2), Sutrakritanga (Option 3), and Brihatkalpasutra (Option 4) are all important texts within the Jaina tradition.