A piece of metal is acted on by a force that rises to a maximum value and then returns to zero. A force-extension graph for the piece is shown. As the piece contracts, it retraces the same force-extension curve as during stretching. What behaviour does the metal show between $X$ and $Y$?
- Aboth elastic and plastic
- Bnot elastic and not plastic
- Cplastic but not elastic
- Delastic but not plastic