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。
If you are walking away from a clock tower ，you will hear the ticking of the clock fade to a point ________ it cannot be heard.
EmpiricalstudiesshowthattheprocessofSLAisaprocessofconstructingandmodifyingrulesofcommunication.
InclassifyingtheEnglishconsonantsandvowels,thesamecriteriacanbeapplied.
Thereply,whenitfinallycame,was________thenegative.
He talked a lot about things and persons ________they remembered in the school.
