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。
Children have a natural ________ about the world around them.
The other timing system belongs in our internal clocks，which，left ________，would tie the body to a 25-hour rhythm.
EmpiricalstudiesshowthattheprocessofSLAisaprocessofconstructingandmodifyingrulesofcommunication.
We ________ go out to restaurants, but mostly we eat at home.