100 г азота, содержащего в качестве примеси CO2, последовательно 5 раз пропускали через слой угля при 800°С и слой оксида меди при 500°С

We shall spend our holidays in Great Britain,shall not we?
The girl helped her mother about the house last week,didn't she?
I never play tennis in winter, do I?
You are not a doctor, are you?

We shall spend our holidays in Great Britain,..shan't we?
The girl helped her mother about the house last week,...didn't she...?
I never play tennis in winter,..do I...?
You are not a doctor,..are you..?