Paragraph Three Tears have a more complex chemical composition than was imagined and they might act as one of the body's waste disposal system. Evidence from tear research may warrant a drastic change in our thinking about crying. Although there is such a thing as people weeping to excess, crying in response to various emotions is a natural physical process that we should not be ashamed of. It is not a shame to let the tears f______.
【正确答案】：flow
【题目解析】：该段讨论了眼泪含有复杂的化学物质而且流泪是一种自然的物理过程，流泪不应该觉得害羞。可以概括为“让眼泪流出来不是一种耻辱”，空白处缺少的是“流出”的意思，flow符合题意。
