I have been practicing grammar structures of various modal verbs (from the Thomson/Martinet structure drills exercise book) and I have come across this one exercise that left me pretty confused.
The exercise is aimed at practicing two structures:
should + continuous infinitive (i.e. I should be doing)
should + continuous perfect infinitive (i.e. I should have been doing).
In the exercise, you are given 20 sentences and you have to transform them, using both structures—continuous inf. and perfect continuous inf. The example given made it pretty unclear for me when should I use which structure. It goes like this:
A: It's 7.20 and Ann is sleeping.
B: She shouldn't be sleeping. She should have been getting dressed.
A: At 7.20 yesterday Ann was sleeping.
B: She shouldn't have been sleeping. She should have been getting dressed.
So, my question is: Why is should + perfect continuous used in (ONE)?
In my understanding "should + continuous infinitive" would be the correct structure, as in:
"She shouldn`t be sleeping. She should be getting dressed (now)" ?
Is it an error / a typo or am I missing something here?