问题补充：
Is that the reason you are in favor of Obama for the second round?
A. which
B. why
C. the one
D. for which
答案：
A. which
(答案→)B. why
C. the one
D. for which
解析：考查定语从句的从发。本句陈述句式为that is the reason why you are in favour of Obama for the second round. Reason 是后面定语从句所修饰的先行词，在从句中做原因状语。相当于for which
