The correct option is A Akhil Bhartiya Vidhyarthi Parishad
The BJP is a cadre-based party. It has close connections with other organisations with similar ideology, such as the Rashtriya Swayamsevak Sangh and the Vishva Hindu Parishad. The Akhil Bharatiya Vidyarthi Parishad (All India Student's Union), is the students' wing of the RSS. Hence, Option A is correct. The rest of the students' unions are affiliated to other political parties, hence, incorrect.