In which passage is it clearest that the author is using diction to achieve some kind of effect?

AThe teacher stood at the door smiling brightly and welcoming each student to her classroom on the first day of school.

BThe mother gingerly tucked the blanket around her sleepy child and crept like a mouse out the door.

CThe shark's fin moved around the raft, which held four shipwrecked survivors.

DThe dog barked as the mail carrier walked up the stairs and knocked on the front door.