确认一个分词构句的问题
https://imgur.com/a/p3H2hia
(兴大附中考卷)
其中这一句
Instead, straws are typically discarded after a single use, and while they
may be out of sight in garbage bins, they are nonbiodegradable, hence
remaining on our planet for a very long time.
文法没问题，语意也都懂
只是想跟大家确认一件事
“hence remaining...”省略的主词是最开头的“Straws”吗？
应该不是中间那两个“they”吧？！
我大致觉得是这样
但是句子拉太长，然后又有好几个逗号
所以我就不敢这么笃定了
只好询问大家
请知道的人指点一下
谢谢！