1. В том, что мы не ставим перед ним вс глагол don't/doesn't, а используем отрицательную форму глагола (с частицей not).
I am not a doctor [не I don't be a doctor/I don't am a doctor]
We are not doctors [не We don't be a doctor/We don't are a doctor]
He is not a doctor [не She doesn't be a doctor/She doesn't is a doctor]
2. Так же - мы не ставим вс глагол do/does на начало предложения, но ставим одну из форм глагола to be (в зависимости от лица).
Am I a doctor? [не Do I be a doctor?/Do I am a doctor?]
Are we doctors? [не Do we be doctors?/Do we are doctors?]
Is he a doctor? [не Does he be a doctor?/Does he is a doctor?]
3. always (всегда), often (часто), every day (каждый день), every year (каждый год), every week (каждую неделю), usually (обычно), sometimes (иногда), seldom (редко) (подробный список можно посмотреть в Интернете)
Tom has been reading for 2 hours, he has read 44 pages so far.
Rachel has been travelling for three months , she has visited six countries so far.
Patrick has won the national championship four times, he has been playing tennis since he was ten.
Lisa and Sue have made five films since they left college, they have been making films since they left college.
1 have you been playing 2 has broken 3 have you been working 4 have you ever worked 5 has she gone 6 haven’t been waiting 7 has stopped 8 have lost - have you seen 9 have been reading - haven’t finished 10 have read
no, the dog wasnt barking