This is an important problem _______ too few social scientists have researched.
A、whichD
intowhich引導的是problem的定語從句。which指代problem，into與research搭配。
The syntactic rules of any language are ______ in number.
Iaskedhimto________meafewminutessothatwecouldgooveralltheproblems.
Younger children are curious ________ how things work ，and many of them want to take apart everything within their reach.
Thevolunteerswouldrathergobytrainthan________.
The reply, when it finally came, was ________ the negative.
