This is an important problem _______ too few social scientists have researched.
D
intowhich引导的是problem的定语从句。which指代problem，into与research搭配。
Hesaidthatthegroup________himaletterandaskedhimtogothereforaninterview.
Iwaswritingareportlastnight;________Iwouldnothavestayeduplate.
_______forthefreeticket,Iwouldnothavegonetoseefilmsooften.
I asked him to ________ me a few minutes so that we could go over all the problems.
______movesonascaleofthenationallanguage,dialects,andindividualwaysofcommunication.