5. Read and answer. Dmitri Mendeleev was a Russian scientist. He developed the periodic table of elements. Before he presented his work in 1869, he had been studying the properties of elements for a long time. His work helped scientists organise chemical knowledge. a) What did Mendeleev develop? b) What had he been studying before he presented his work? c) Find the Past Perfect Continuous in the text and write what action it shows (what was lasting).

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Dmitri Mendeleev was a Russian scientist. He developed the periodic table of elements. Before he presented his work in 1869, he had been studying the properties of elements for a long time. His work helped scientists organise chemical knowledge.

Дмитрий Менделеев был русским учёным. Он разработал периодическую таблицу химических элементов. Перед тем как представить свою работу в 1869 году, он долго изучал свойства элементов. Его работа помогла учёным систематизировать химические знания.

1. He developed the periodic table of elements. — Он разработал периодическую таблицу химических элементов.
2. He had been studying the properties of elements. — Он изучал свойства элементов.
3. Had been studying показывает длительное действие, которое продолжалось до представления работы в 1869 году. — The form had been studying shows an action that continued for a long time before he presented his work.