[Grammar] Speech part of to infitive

[sky3120]

"Be careful not to fall down."

I still do not agree that 'not to fall down' is an adjective complement. I think that not to fall down modifies careful and it is an adverb and a modifier. not subject, adjective and object complement. What do you native English speakers think?

 

[Tdol]

Most native speakers would have nothing to say on the subject. The majority would be hard-pressed to identify a grammatical form.

 

[5jj]

Most native speakers would have nothing to say on the subject.

And that would include quite a few teachers.