Student or Learner
Can any body please explain me how can I use 'to be able to' in sentence
REMINDER: NOT A TEACHER
(1) As you know, "be able to" and "can" are often interchangeable:
You can speak English very well./ You are able to speak English very well.
(2) I feel that it is important to remember that there are times when it is
(a) According to Raymon Murphy in his very popular book Grammar in Use,
you must use "to be able" when someone managed [was successful] to do
something in one particular situation.
(i) Here is Mr. Murphy's example: The fire spread through the building very quickly,
but everyone was able to escape.
(a) You cannot use "could" in such a sentence. He does not explain why. I think that
I know, but as a non-teacher, I must be careful not to give wrong information.
Hopefully, a teacher will give us learners the reason.