David had prepared carefully for the chemistry exam, as he wanted to be sure of passing it

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A. experiment
B. intention
C. aim
(答案→)D. attempt
解析：考查名词辨析。句意：大卫已经为化学考试做了精心准备，因为他想确定第一次尝试就通过。A实验；B意图，目的，打算；C目标，目的；D尝试，企图。“化学考试”不是一次实验，排除A；B、C两项在此与句意不符；at the first attempt初次尝试，故选D。