Most parents encourage their children to take an active part in social events, ______ those events do not interfere with their studies.

Most parents encourage their children to take an active part in social events, ______ those events do not interfere with their studies.

1. A.
   concerning
2. B.
   until
3. C.
   unless
4. D.
   provided

Most parents encourage their children to take an active part in social events, ________ those events do not interfere(干擾)with their studies．

1. A.
   as though
2. B.
   until
3. C.
   unless
4. D.
   so long as

 Most parents encourage their children to take an active part in social events,________ those events do not interfere (干擾) with their studies.

   A.as though           B.until         C.unless    D.so long as

Most parents encourage their children to take an active part in social events, ______ those events do not interfere with their studies.