There is no chances for bonus marks as this year bonus marks were not the part of the evaluation.However, a possibility of bonus marks being awarded still exists if challenges to the answer key as initiated by candidates and coaching experts are accepted by the CBSE. Deadline to submit challenges was May 27, 2018. Now CBSE will look into all the challenges and consider them. Subject experts will review the answers and decide on finalizing answers. This decision will be final.
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https://news.careers360.com/neet-2018-official-answer-keys-and-omr-sheets-released-no-bonus-marks-awarded