For today's Geo Quiz, find the longest river in Asia.

Only the Nile in Africa and the Amazon in South America stretch out longer than the river we're looking for. Its waters flow out of the Qinghai Province in China.

Then the river meanders 800 miles before emptying into the East China Sea at the port of Shanghai. This river roughly divides north and south China. An international team of scientists surveyed this river to find an elusive species of dolphin called the Baiji.

They didn't find any. Researchers now believe this freshwater dolphin fell victim to overfishing, pollution and river traffic.

We'll tell you more about the Baiji when we reveal the answer later in the program.