Read this excerpt from a poem.

Anticipation is a grip on their hearts;
They wait with frozen smiles
Until it finally starts.
With a je.rk, their cart begins to climb
And every click of the chains
Pric.kles their spines.

Which line contains a metaphor?

Anticipation is a grip on their hearts;
They wait with frozen smiles
With a jer.k, their cart begins to climb
Pr.ickles their spines.