题目分析：
略

选项分析：

选项A：Correct. 本选项在语法和逻辑上均是正确的。

选项B：when placing them with others of their species是伴随状语，其主语必为主句的主语，即，蝗虫（they）。在逻辑上，放置蝗虫的不能是蝗虫本身。

选项C：when placed with others of their species身前出现了名词locusts，在划线部分身后又出现了完整句子they become excited, change color, vibrate, and even hum，这造成了同一个句子有两个主语的情况。

选项D：分词短语placing them with others of their species是伴随状语，其逻辑主语错误同选项(B)。

选项E：伴随状语placed with others of their species和其主句placed with others of their species之前不能出现副词then，只有if可以和then连接。

展开显示