3. Make the sentence. Use the Past Perfect Continuous. a) Kovalevskaya / study / mathematics / for years (утверждение). b) Researchers / not / conduct / experiments / since May (отрицание). c) Tsiolkovsky / work / on his ideas? (вопрос).

Перевод задания: Составьте предложения, используя Past Perfect Continuous.

1. Kovalevskaya had been studying mathematics for years. — Ковалевская изучала математику много лет.

2. Researchers had not been conducting experiments since May. — Исследователи не проводили эксперименты с мая.

3. Had Tsiolkovsky been working on his ideas? — Циолковский работал над своими идеями?