[Grammar] must have been watching and must have watched

[tom3m]

If we are to transform a sentence like this:

I am sure that he was watching the film, before she came.

Which option is better to express the same as the sentence above?

1) He must have watched the film...

2) He must have been watching the film...

I'd say the second is correct.

Thank you in advance

 

[Tdol]

I would use the second too.