3. which sentence uses dashes correctly?

a.
turquoise beads and—a silver medallion—adorn her favorite necklace.

b.
several birds stayed at the feeder—hoping for a good meal.

c.
"i would not step there if i were—! " she began as i slipped on the wet floor.

d.
my sister—a big fan of the outdoors—walks two miles—every afternoon.