Paragraph Ten Usually a combination of causes produces a result. People need to distinguish between necessary and sufficient conditions. Air is a necessary condition for the maintenance of plant life, but air alone is not sufficient to produce plant life. Different causes at different times may produce the same result.Many causes may l______to the same result.
【正确答案】：lead
【题目解析】：根据文章：“Different causes at different times may produce the same result.”可以得出答案。
