Which sentence uses dashes correctly?
a. everyone enjoyed the show—and gave a standing ovation—to the players.
b. a complex assignment—that is, one that requires research—usually takes a few days to complete.
c. my aunt's quilt was the most colorful one—red and purple—in the fair's quilting exhibit.
d. they use the same—decorations every year—i'm hoping they make new ones this time?