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。
It is not decided ________ the conference will be held.
It was a small place then compared to _______ it is now.
By "language acquisition is primarily the acquistion of the grammatical system of language", linguists mean that ______.
He talked a lot about things and persons ________they remembered in the school.
Bloomfield drew on ______ psychology when trying to define the meaning of linguistic forms.
