英语翻译there's no telling to do

Question

There's no telling to do什么意思？大学学的
There is no telling when he will return.说不清他何时回来。There is no telling when the train will arrive.说不上火车什么时候到。There is no telling when they can get ready.他们什么时候能准备好还没法说。There is no telling where he is.无法知道他到底在哪里。

Answer 1

有没有人知道做there is no+doing是固定搭配
没有说他要去做什么.

Answer 2

没有说要做