Which sentences have used synecdoche？

Which sentences have used synecdoche？
A.Foodistothebodyasfuelistotheengine.
B.He is a valiant heart.
C.Thekettle boils.
D.Thefoxgoesverywellwithyourcap.
正确答案：He is a valiant heart.Thefoxgoesverywellwithyourcap.