Cora and Mellie held hands so tightly, their fingers were a chain-link fence.

Which statement best interprets the meaning of this metaphor?

a
Cora and Mellie’s hands are bound together by a chain.
b
Cora and Mellie’s hands are grasped strongly together.
c
Cora and Mellie’s hands look like a metal fence.
d
Cora and Mellie’s hands are made of metal.