The Admissions Officer wants to know that you have thought through all options and scenarios if you do not earn acceptance into Boston University's speech-language pathology program. Your answer to this question should show the admissions team that your interest in the speech pathology field goes deeper than your acceptance into their school.
If you are not accepted, show the admissions team that it will not be the end of your journey. Perhaps you would take the time to upgrade, apply to new schools, or entertain a different path as a speech pathology assistant or researcher. Alternatively, you can let the interviewers know that one rejection won't stop you. Talk about your plan to qualify yourself better and reapply when you're ready. Whichever way you respond, be sure to show the interviewers that you have the confidence and drive to achieve your goals.