Invention can be as it may suddenly begin just by noticing something usual.
A. accidental
B. careless
C. necessary
D. imaginative
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(答案→)A. accidental
B. careless
C. necessary
D. imaginative
解析：A 考察形容词辨析。Accidental偶然的，careless粗心的；necessary必要的；imaginative虚构的，富于想象的；根据suddenly可知A正确。句意：发明有时也是偶然的，因为它仅仅开始于注意到了某个平常的某个东西。故A正确。