Answer:
Biologists backed up these ideas with sketches and models based on known animals.
Explanation:
The sentence from paragraph 4 which makes an explicit statement without offering any implicit suggestions is Biologists backed up these ideas with sketches and models based on known animals.
From the excerpt, the narrator is talking about how a dragon would have been like, how its stomach would have been like if it could actually fly and spit out fire.
The narrator is unsure of what to believe but he says that when the animal died, then its stomach could release strong acids which would dissolve its carcass over time and made the explicit statement that biologists have backed up the ideas based on known animals, even if not everybody agreed with their ideas.
