Global Health officials have been closely monitoring a new virus related to SARS that is believed at least one person in Saudi Arabia．
A. to kill
B. to be killing
C. to have killed
D. kill
网友回答
A. to kill
B. to be killing
(答案→)C. to have killed
D. kill
解析：考查非谓语动词中不定式用法。本题考查了believe的固定搭配，be believed to do sth，如果不定式的动作是已经完成的动作，就是还有完成时to have done;如果是被动关系就使用被动式to be done。句意：世界健康官员一直都在监视一种新型的与SARS有关的病毒，这种病毒据说已经杀死了至少一个人。故该句表示的是已经完成的动作，故C正确。