You are welcome to answer questions posted in the Ask a Teacher forum as long as your suggestions, help, and advice reflect a good understanding of the English language. If you are not a teacher, you will need to state that clearly at the top of your post. Please note, all posts are moderated by our in-house language experts, so make sure your suggestions, help, and advice house the kind of information an international language teacher would offer. If not, and your posts do not contribute to the topic in a positive way, they will be subject to deletion.
Have a look what the CALD has to say: burn your boats/bridges
If you are in a situation and you burn your boats/bridges, you destroy all possible ways of going back to that situation.
Here, the question is about adapting the idiom to a contet- idioms are not cast in stone and we can change and adapt them for specific contexts. If you didn't have the word 'that' (or 'those') in the sentence, you wouldn't need to adapt, but once you refer specifically to the thing left, then it changes the context.
Singular or plural idea here? 
Linear Mode
