Which sentence uses a comma correctly to set off an introductory phrase?

a. the innkeeper, who was not very friendly, slid the room key across
the desk.

b. the music, dancing, and costumes make this performance an
unforgettable experience.

c. even, two weeks later daniel was complaining about losing the
match

d. to make matters worse, blake and tricia were now locked out of
the house.

the correct answer can either be a or b because it could be both but you should probally choose b

b. cronkite, a trusted television personality, declared that the war was unwinnable and told the american people that the government had better find a way out

even though it went against everything the news anchors typically stood for, cronkite voiced an opinion and took a stance, telling the us that there was no way they were going to win, the war was going to end in a stalemate.