Take a look at this passage from "Bird Brains? Not These Birds!" Choose two sentences that support the idea that rooks can solve complex problems using tools. British scientists Christopher Bird and Nathan Emery did the study. They showed a 6-inch-tall clear plastic tube to four rooks. The tube contained some water. A worm was floating on the water. But the birds could not reach the worm. Each bird used the stone-dropping trick on its own. The birds also appeared to estimate how many stones they would need