t contains entries for
   <ul>
   <li>Default
   <li>1.0
   <li>1.1
   <li>2.0
   <li>4.0
   </ul>

<p>If you select "Default" the assemblies in the project are examined to determine
   the version that is required.
   See <a href="runtimeSelection.html">Runtime Selection</a> for
   more information on how NUnit selects the version to be used.

<p>In special cases, you may wish to enter a version number that is not listed
   in the list box. You may specify the version using two, three or four
   components