I'm assuming there's a time limit, but yes, you can do two (or more) pieces from the same composer - you can even do two (or more) parts of works by the same composer.I'd suggest strongly that if you are going to take that option, there be a clear relationship between the pieces that makes the selection inherently interesting and reasonable - such as showing compositional development, or how a similar idea could be used to create very different works, or some such. Just picking two or more pieces at random - because you like them, or because they are the flashiest, for example - would not really work, though would be within the rules.