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

问题补充：

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

A. experiment

B. intention

C. aim

D. attempt

答案：

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。