Bengali is the most important of those subjects. You have to answer 35 bangali questions out of total 200 questions. Here we suggest you some bengli books for your perfect preparation.
For long and healthy preparation you may follow - Oracle BCS preliminary Bangla.
For short and Quick preparation you may follow - MP3 BCS Preliminary Bangla.
Both of students must follow Sahitto Jiggasha by Saumittra Shekhor.