问题补充：
Our special thanks go to thousands of volunteers, without tireless work, none of this would be possible．
A. whose
B. which
C. whom
D. that
答案：
(答案→)A. whose
B. which
C. whom
D. that
解析：句意：非常感激成千上万的志愿者们，没有他们不知疲倦的工作，这些都是不可能实现的。整个句中有两个主语，两个谓语，句子必须要有连接词。whose谁的，在定语从句中做定语修饰主语或是宾语。故选A.
