问题补充：
We do have the most supportive parents and teachers, will make a difference to our study, unless all of us make every effort .
A. none of them
B. all of them
C. none of whom
D. all of whom
答案：
A. none of them
B. all of them
(答案→)C. none of whom
D. all of whom
解析：句意：我们有最支持我们的父母和老师，如果我们不努力，谁对我们的学习也没有多大的作用。逗号前后都是句子，这里缺少连词，故排除AB；这是定语从句，先行词是parents and teachers，从句缺少的是主语，none of whom他们中没有；all of whom他们所有的人，根据句意故选C。
