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。
______ofasentencedependsonthecontextinwhichthesentenceisuttered.
ThedivisionofEnglishintoOldEnglish,MiddleEnglish,andModernEnglishisnonconventionalandnotarbitrary.
Theothertimingsystembelongsinourinternalclocks,which,left________,wouldtiethebodytoa25-hourrhythm.