1.public speaker 公共演说家；发言人

例句：Faith in yourself, your topic, and your general sanity is a must if you are to be a better public speaker.
要对你自己和你的主题有信心。 如果你要做一个更好的公众演讲者你必须保持清醒的头脑。

2.conducted 从事；引导；负责；管理

例句：You must choose what best suits the operation being conducted.
您必须选择好什么时候最适合进行操作。
3.toxic substances 有害物质；有毒物质

例句：Avoid placing water containers in areas where toxic substances, such as gasoline and pesticides, are present.
避免将食水的容器存放在靠近有毒物质的区域内，如汽油和杀虫剂。

4.clean up 清除；打扫；收拾干净

例句：Under pressure from the public, many regional governments cleaned up their beaches.
迫于公众的压力，许多地区政府治理了海滩污染。