Which Siberian river, over 4,400 kilometres long, forms a vast delta that empties into the Laptev Sea in the Arctic Ocean?

• A The Lena ✓
• B The Ob
• C The Yenisei
• D The Amur

The Lena is one of the three great Siberian rivers flowing north into the Arctic; its delta covers about 30,000 square kilometres and is a major breeding ground for migratory birds.