How can I make this sentence politer? Hi. I have read this sentence: この山を登るのは危険だ。 And I was wondering how to make it politer. But I'm not sure if the particle の can be used after ます and I think, if I use the ます form I must change the だ by です too, to keep all the sentence polite. So, my question is, which of these sentences are correct to make that sentence politer? この山を登りますのは危険だ。 この山を登りますのは危険です。 この山を登るのは危険です。 Thanks in advance.