What is a difference between alligators and crocodiles?
A difference between alligators and crocodiles is the shape of their heads. Crocodiles have more narrow and longer heads than alligators.
Instruction: What is a difference between alligators and crocodiles?
Context: 
Response: A difference between alligators and crocodiles is the shape of their heads. Crocodiles have more narrow and longer heads than alligators.