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<p>A student who starts in engineering can usually switch to math or physics pretty easily, even after 3 or 4 semesters. Some humanities and social studies majors which do not have long prerequisite sequences can be switched to easily also (especially if a freshman year breadth requirement course were used for a course in that subject).</p>
<p>A student who explores in the first two years needs to be careful to take the needed prerequisites in time for any major that s/he might declare, in order to avoid accidentally shutting himself/herself out of some potentially interesting major. For example, switching into engineering or physics after a few semesters is likely to result in delayed graduation if the student has not been taking math and physics courses.</p>