<p>That is because they are already aware that you have pre chosen an impacted major i.e Mech. Engineering through TAG. What they are requesting from you is an alternative major choice. If you do not state you will be deemed an ‘Undeclared Major’ student. Just declare a non impacted Engineering major as your alternative so gives them some indication you are serious about attending UCSD and willing to be patient for a seat to open up for you in ME.</p>