Thisisanimportantproblem_______toofewsocialscientistshaveresearched.

The engineer ______ my father works is about 50 years old.

Theengineer______myfatherworksisabout50yearsold.

Accordingtothe"principles-and-parameters"theory,"principles"refertohighlyabstractpropertiesofgrammarwhichareappliedtolanguageingeneralandwhichgeneratephrasesandatthesametimerestrainthepowerofMovea,while"parameters"allowgeneralprinciplestooperateincertainrestrictedways,accordingtowhichparticulargrammarsofnaturallanguagesvary.

Theconclusionfromthestudyisnotdefinite;itisjust________.