The Nuclear Security Summit is an initiative of Mr. Obama, considers nuclear terrorism to be one of the greatest threats to international security.
A. which
B. what
C. who
D. whom
网友回答
A. which
B. what
(答案→)C. who
D. whom
解析：句意：核安全峰会是奥巴马先生的计划,他认为核恐怖主义是对国际安全的最大威胁之一。这句话使用了定语从句，先行词是Mr. Obama，定语从句中缺少主语，用who引导定语从句，所以选C。