Exam for BA program is mix of both objective and subjective where 50marks subjective questions like Short essays can be asked.
Objective questions willbe based on reasoning, grammar, language and Comprehension .
Exam pattern given below.
https://university.careers360.com/articles/jnu-exam-pattern
Book by R. Gupta is decent and sufficient however you should also refer to JNU Ba Hons Entrance exam solced papers by Arihant Publications .
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