On Being Solute
by Jon Caswell

Sea foam races toward shore,
marking the tide on the beach,
where sand and sea intermingle
to create luminous pink bubbles.
A colony of them floats on the waves
with the aplomb of a bull-rider—
only to be left stranded at high tide.
Evanescent bubbles populate the beach
in iridescent mounds, effervescing
out of turbulence only to evaporate in the wind
or melt back into the surf.
Do they perceive themselves?
Do they devolve or progress?
Do bubbles aspire and transcend,
or are they just form—
subdividing nothing into something?

Which of these lines contains a metaphor?
A.
"out of turbulence only to evaporate in the wind"
B.
"A colony of them floats on the waves"
C.
"only to be left stranded at high tide"
D.
"a moment without time, mind you,"

I think it's either B or C. Please explain why it is!