4 With renewed hope that there was some truth to the legends, I looked for new research. I found that some experts disagreed with popular arguments against dragons. They suggested that a dragon could have four stomachs like a cow. If it created stomach gases like birds, it might create enough to lift itself off the ground. This would give it the ability to fly. If it forced out air when diving toward the earth, it might release gases which could ignite into flame. When the animal died, the stomachs would release strong acids that would dissolve its dead body over time. Biologists backed up these ideas with sketches and models based on known animals. Not everyone agreed with these ideas, but many of the things we accept about dinosaurs and other extinct species started the same way.

Which sentence from paragraph 4 makes an explicit statement without offering any implicit suggestions?
1. With renewed hope that there was some truth to the legends, I looked for new research.
2. If it created stomach gases like birds, it might create enough to lift itself off the ground.
3. Biologists backed up these ideas with sketches and models based on known animals.
4. Not everyone agreed with these ideas, but many of the things we accept about dinosaurs and other extinct species started the same way.