For 20th C, look at some Bartok.
Do you know any other Bach? Perhaps something a bit more difficult. Like a Sinfonia, a movement from one of the dance suites, or a Prelude and Fugue? Invention #1 is well known and a bit on the easy side for a university audition.
You could also go with other Baroque composers such as Scarlatti, Soler, Daquin, Couperin, or Clérambault.