His laziness his failing in the exam.
A. result from
B. accounts for
C. because of
D. is on account of
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A. result from
(答案→)B. accounts for
C. because of
D. is on account of
解析：考查词组：A. result from源于B. accounts for是…的原因C.because of 因为D. is on account of由于，句意：他的懒惰是他考试不及格的原因。选B。