Who among the following started the Shuddhi Movement to promote reconversion and social reform within Hindu society?

Introduction / Context:
This question is about social and religious reform movements in modern India. The Shuddhi Movement was an important effort aimed at reconversion of people to Hinduism and at removing certain social evils. It is closely linked with the Arya Samaj, a reformist organisation that sought to return to what it saw as the pure original principles of the Vedas. Identifying the founder of this movement helps anchor your understanding of reform currents in nineteenth century India.

Given Data / Assumptions:
- The movement named is the Shuddhi Movement.
- The purpose was reconversion and social reform within Hindu society.
- Several well known Indian spiritual and political leaders are listed as options.
- Only one of these leaders is historically recognised as starting the Shuddhi Movement through the Arya Samaj.

Concept / Approach:
The central concept here is to connect the Shuddhi Movement with the Arya Samaj. The Arya Samaj was founded by Swami Dayananda Saraswati in 1875. It emphasised a return to Vedic teachings and opposed idol worship and caste based discrimination. The Shuddhi Movement emerged from this context as a programme to bring people who had converted to other religions back into the Hindu fold and to raise the status of oppressed groups. Therefore the correct answer must be Swami Dayananda Saraswati as the originator of this broad reform approach, even though later leaders such as Swami Shraddhanand also played major roles in Shuddhi campaigns.

Step-by-Step Solution:
Step 1: Recall that Shuddhi literally means purification and in this context refers to religious reconversion and reform.Step 2: Link the Shuddhi idea with the Arya Samaj, a reformist Hindu organisation.Step 3: Remember that Arya Samaj was founded by Swami Dayananda Saraswati, who promoted Vedic principles and opposed caste oppression.Step 4: Recognise that later Arya Samaj leaders, like Swami Shraddhanand, vigorously carried forward Shuddhi campaigns, but the movement originated with the vision of Swami Dayananda Saraswati.Step 5: Compare this understanding with the options and select Swami Dayananda Saraswati as the correct answer.

Verification / Alternative check:
You can verify by thinking of key slogans and organisations. Swami Dayananda Saraswati gave the call India for Indians and founded Arya Samaj. Textbook descriptions of the Shuddhi Movement usually mention it as a programme initiated by Arya Samaj under his inspiration, with later expansion under his disciples. None of the other personalities in the options is primarily associated with founding Arya Samaj or initiating Shuddhi on an all India basis.

Why Other Options Are Wrong:
- Sri Aurobindo: He was a revolutionary and spiritual thinker, but he is not linked with founding the Shuddhi Movement or running large scale reconversion campaigns.
- Swami Vivekananda: He emphasised spiritual strength and social service through the Ramakrishna Mission, not Shuddhi style reconversion.
- Yashoda Bhai: This name does not correspond to a widely known leader of any major nineteenth century reform movement.
- Swami Shraddhanand: He was a major Arya Samaj leader who actively conducted Shuddhi campaigns, but he worked within the framework first created by Swami Dayananda Saraswati, not as the original founder.

Common Pitfalls:
A typical mistake is to choose Swami Shraddhanand because many accounts mention him prominently in connection with Shuddhi in the early twentieth century. The exam, however, usually expects you to identify the broader founder of the movement and organisation, which is Swami Dayananda Saraswati. Another pitfall is to confuse Shuddhi with general Hindu revival efforts by other leaders like Swami Vivekananda, whose focus was somewhat different.

Final Answer:
The Shuddhi Movement to promote reconversion and social reform within Hindu society was started by Swami Dayananda Saraswati through the Arya Samaj.