This is an important problem _______ too few social scientists have researched.
A、whichD
intowhich引导的是problem的定语从句。which指代problem，into与research搭配。
Theengineer______myfatherworksisabout50yearsold.
Thebasicunitinthestudyofmorphologyis______.
Bloomfielddrewon______psychologywhentryingtodefinethemeaningoflinguisticforms.
Thisisanimportantproblem_______toofewsocialscientistshaveresearched.
ModernEnglishwordsman,woman,child,eat,fight,etc,originatefrom______.
