According to the Mimamsa system of philosophy, liberation is possible by means of Option 4: Karma. The Mimamsa school of philosophy, also known as Purva Mimamsa, is one of the six orthodox schools of Hindu philosophy and focuses primarily on the interpretation of the Vedas, particularly the ritualistic and ethical aspects.

Mimamsa philosophy emphasizes the importance of performing prescribed rituals and fulfilling one`s duties, known as karma. It holds that liberation or moksha can be attained through the proper performance of these karmas without relying on any external factors such as divine grace or personal devotion.

The Mimamsa system argues that the Vedas are eternal and authoritative, and their injunctions and rituals are a means to achieve desirable results, both in this world and the afterlife. The performance of karma, in accordance with the prescribed rules and regulations of the Vedas, is seen as a path to purification and liberation.

The concept of karma in the Mimamsa system involves performing actions selflessly and without attachment to the outcomes. It emphasizes that individuals should focus on their duties and responsibilities without seeking personal rewards or benefits. The performance of karma is believed to purify the mind, develop self-discipline, and cultivate a sense of duty and righteousness.

Additionally, the Mimamsa system emphasizes the idea of svarga (heavenly realms) and apurva (unseen results) that are generated through the performance of rituals. It is believed that the accumulation of positive karma through the proper performance of rituals leads to favorable future outcomes and ultimately liberation from the cycle of birth and death.

While the other options mentioned in the question, such as Jnana (knowledge), Bhakti (devotion), and Yoga (spiritual practice), are indeed important in various other philosophical systems of Hinduism, the Mimamsa system primarily focuses on karma as the means of attaining liberation. It places great significance on the correct performance of rituals and fulfilling one`s duties as prescribed in the Vedas.

It`s worth noting that different schools of Hindu philosophy may offer different perspectives on the means to liberation, and individuals may find different paths more suitable to their spiritual inclinations and temperament.