Which lines contain a metaphor?
a. "and left behind her, / bead upon bead, / the track of small feet / like dark fern seed."
b. "like a queen who walks / down a corridor / the black cat paced / that cold smooth floor—"
c. "and the lamplight fell / narrow and thin / a carpet unrolled / for the cat to walk in."
d. "slowly, smoothly, / black as the night, / with paws unseen / (white upon white)"