1·They may not have verbs, nouns or past participles, but birds challenge the notion that humans alone have evolved grammatical rules.
它们可能没有动词、名词和过去分词，但是鸟类挑战只有人类演化出语法规则这一观念。
2·Note that the past participles of irregular verbs do not end in '-ed', but can be used as adjectives.
注意：不规则动词的过去分词，不能加“- ed”，但可用作形容词。
3·The topic being discussed is participles.
正被讨论的话题是分词。