Ответ:

By 10 o'clock the kids hadn't done their homework

Had the kids done their homework by 10 o'clock

Little Johnny hadn't been riding his bike all day yesterday

Had little Johnny been riding his bike all day yesterday?

I hadn't finished writing a letter

Had you finished writing a letter?

a) had watched

b) had been watching

a) had built

b) had been building

a) had flown

b) had been flying

Объяснение: