2. Complete the sentences. Use the Past Perfect Continuous. 1) Before the experiment ended, the scientists (work) for six hours. 2) He (study) mathematics since he was a child. 3) They (not / use) the new method for long.

Перевод задания: Дополните предложения. Используйте Past Perfect Continuous.

1. Before the experiment ended, the scientists had been working for six hours. (До окончания эксперимента учёные работали уже шесть часов.)
2. He had been studying mathematics since he was a child. (Он изучал математику с детства.)
3. They had not been using the new method for long. (Они использовали новый метод недолго.)

В отрицании перед been ставится not.