Question

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

Answer 1

C

试题分析：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。