Greetings aspirant,

Not just WBJEE, but all competitive exams have rules and guidelines for bonus marks. Most of them give bonus marks under the following conditions:

1) There is a misprint in a particular question of the exam paper which wasn't resolved before conclusion of that exam.

2) There are no correct answer in the provided options for that particular MCQ question.

3) If there are multiple correct answers to a single correct type question.

Good luck.