If your answer does not match one of the options it is probably wrong.
The best exam strategy is to skip the question, answer the rest of the paper, and then go back and make a clean start on it in the time you have left at the end of the exam.
If there is no time left just go for your best guess.
As a general exam strategy it is always best to read the entire paper, first then answer the questions that you are certain of the right answer then move on to the more difficult ones, leaving the hardest until last.
Answering the rest of the paper will often give you a clue or a reminder for the difficult question.