问题补充:
A survey was carried out on the sleep time of students in middle schools, were surprising.
A. its results
B. whose result
C. the results of which
D. of which results
答案:
A. its results
B. whose result
(答案→)C. the results of which
D. of which results
解析:考查定语从句。题中the results of which = whose results,故选C。