There's no knowing

[Neil kevin]

Test No. incompl/elem-30 "Responses (3)", question 7

Mike: 'I wonder what she'll get up to next.'
Jane: '.........'

(a) There's no finding.
(b) There's no knowing.
(c) There's no guessing.
(d) There's no seeing.

Test No. incompl/elem-30 "Responses (3)", answer 7

Mike: 'I wonder what she'll get up to next.'
Jane: 'There's no knowing.'

Correct answer: (b) There's no knowing.

Your answer was: incorrect
Mike: 'I wonder what she'll get up to next.'
Jane: 'There's no guessing.'
_________________________

Pls, explain for detail why we use knowing in this case.?
As I learned the word Know have no form of V-ing
Many thanks for you reply.

[Alan]

This means it is impossible to say/tell.
_________________
English as a Second Language
You can read my ESL story If you vote