Captivate is not a presentation tool like Powerpoint, it is meant to create eLearning courses.
You can publish a non-responsive project with the setting 'Scalable HTML'. When the learner resizes the browser, the course will adapt to the available pixels, but without distorting the width/height ration of course. Difference with a responsive project is that the course needs to be viewed preferably in landscape mode.
You can find more about the differences between the 3 ways to have a course adapting to the browser resoltu!ion in:
Thank you for your reply. It helped. Once again thank you very much, also for sending me to your blog - I learned few additional things there.