Which animal carries their babies on their backs and swims in rivers?

Otter

Which volleyball move involves hitting the ball forcefully downward onto the opponent's floor? What Hungarian Christmas sweet treat is a rolled pastry filled with walnuts or poppy seeds? Which thick dairy product is often used in baked cheesecake recipes? Who was the first player ever to average a triple-double for a full NBA season? Who was the first woman prime minister of India?