6. take 7. urging

I would choose urging, but to answer your question propose would mean to suggest a plan or course of action, suggest would mean to imply, but not say explicitly what you want. It’s a subtle difference

urging

The answer is 'urging' - urging city developers to use.... - suggesting (that) city developers use... - proposing (that) city developers use... A suggestion is something that you think will be a good idea for someone to do A proposal is like a plan, or an idea that has been thought about in advance that you put forward, for agreement or not... It would probably be more well-defined then just a suggestion which tends to be a more spontaneous idea...

The answer is urging. It is the only option that requires no further words to be added If you use suggesting or proposing you need to say proposing that, suggesting that Suggest and propose are synonyms in terms of meaning although in practice you wouldn't use suggest for marriage although the meaning would be the same