Context: He 's crouched down , close to the ground , sniffing it cautiously . Then he lifts his nose to the air once more , turns his head either way , and inhales deeply . Then he lets out a small growl and turns to the other three while on all fours .
Question: What may be a fact about this situation ?
Option 0: A dog is getting aggressive .
Option 1: A dog has discovered something .
Option 2: None of the above choices .
Option 3: A dog is ready to attack .
Answer: 1