The question paper for your regional language (Bengali in this case) in CUET will most likely be only in Bengali.  The regional language section of CUET assesses your proficiency in your chosen regional language. Bengali questions in Bengali allow for a more accurate evaluation of your Bengali language skills.

CUET offers regional language options to cater to students from diverse linguistic backgrounds. Having the question paper in the chosen regional language ensures a fair assessment for everyone.

https://university.careers360.com/download/ebooks/all-about-cuet

I hope it helps!