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。
InclassifyingtheEnglishconsonantsandvowels,thesamecriteriacanbeapplied.
Weather_______,we’llgooutforawalk.
Theconclusionfromthestudyisnotdefinite;itisjust________.
Lyingundertheskull,thehumanbraincontainsanaverageoftenbillionnervecellscalled______.
Hetalkedalotaboutthingsandpersons________theyrememberedintheschool.
