You can attempt a question as many times as you like.
If you are logged in, your first attempt, each day, is logged.
To improve your scores, come back on future days, log in and re-do the questions that caused you problems.
If you are logged in, your most recent wrong answers get remembered. This might help you and your teacher to correct your understanding.
In the grade book, you can delete your answers for a topic before re-doing the questions. Avoid deleting unless you intend re-doing the questions very soon.