Yes. You can mark a question for 'review' and revisit it anytime during the exam. You can use this feature to your advantage.
Tip: If you are not sure about the answer of a particular question, just go by your instincts or your best guess and select an answer. Mark this question for review. Complete the first pass of all the (200) questions and then revisit the questions marked for review, at the end.
Note: Don't forget to bookmark this site.