Which sentence uses dashes correctly?

a.
we had one thing in mind: swimming—in the ocean.

b.
the phone—just kept ringing and ringing all afternoon.

c.
the music teacher gave him a choice of horns—for example, the trumpet, the tuba, or the saxophone.

d.
a red chair sat in front of—the fireplace.

Correct the sentence below: the pizza delivery boy was neither early nor late he was right on time. a: correct as it is b: the pizza delivery boy was neither early nor late, he was right on time. c: the pizza delivery boy was neither early nor late; and he was right on time. d: the pizza delivery boy was neither early nor late: he was right on time.