It is noteworthy in this scenario that the original, thorough laboratory investigation failed to find any assignable cause. 值得注意的是此假想有一个前提,即在初始的完整化验室调查中,并未发现任何可归结原因。
The unknown and unpredictable element in happenings that seems to have no assignable cause. 偶然性在似乎无因可查的事件中末知和不可预测的成分。