This maybe a bit of Chinglish thinking.
For example you can say
It can be a [noun]
It's possible that this is a [noun]
Using pain as an example:
If you want to say the opposite, not sure should you say
It can not (to?) be a pain
since that feels like "It's not a pain" but not what I want to express:
It's possible that it is not a pain
I think this might be a better example:
I want to express the opposite of
You can choose this one
You can choose not to choose this one
But I am after a shorter version of it.
I feel one way would be to say
You cannnnnnn, short pause, not to choose this one