

Учёные долго исследовали эту проблему.
Scientists studied this problem for a long time.
Мы хотим исследовать рынок перед запуском продукта.
We want to research the market before launching the product.
Эту пещеру ещё никто не исследовал.
No one has explored this cave yet.
"исследовать" is in the lesson "Verbs 14" (Level 26), along with 10 other useful words. LinDuo has 180 topic lessons like this one, 2,380 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.