Thisisanimportantproblem_______toofewsocialscientistshaveresearched.
A、whichD
into which 引导的是 problem 的定语从句。 which 指代 problem ，into 与 research 搭配。
Thevolunteerswouldrathergobytrainthan________.
Linguistscanconcentrateonalltheaspectsoflanguageatonce.
By"languageacquisitionisprimarilytheacquistionofthegrammaticalsystemoflanguage",linguistsmeanthat______.
_______forthefreeticket,Iwouldnothavegonetoseefilmsooften.
______movesonascaleofthenationallanguage,dialects,andindividualwaysofcommunication.
