My father has been a teacher since a few years ago 对 since a few years ago 进行提问
They had to attend the lecture the day before yesterday（改成否定句）
There were few taxis in China at that time （改成反意疑问句）
The plane flies at a speed of 1200 km an hour对at a speed of 1200 km an hour进行提问
l go to Beijing once a year（对once a year进行提问）
when did your father been a teacher
They had not to attend the lecture the day before yesterday
There were few taxis in China at that time ,were there
how far is the plane flies
how often do you go to beijing
When have your father been a teacher?
they had not to attend the lecture the day before yesterday.
were there few taxies in china atthat time?
what does the plane fast to fly?
how long do you go to beijing.
How long has your father been a teacher?
They didn't have to attend the lecture the day before yesterday.
There were few taxis in China at that time ,were there?
How fast does the plane fly?
How often do you go to Beijing?