Answer: "D.
It conveys that Della is leaving to meet someone important."
Explanation: Well,you don't throw on old brown clothes if your going for a cup of tea,there has to be a reason the author included that or else it would never have been there in the first place.I mean,I wear a cool-looking Phadora hat (if I do say so myself) every day but I don't hurriedly throw an OLD one on and go SPRINTING (if you are following my line of thinking WHICH YOU SHOULD,you would notice that you don't go "fluttering" down the stairs every day) AS FAST AS YOU CAN,so fast it looks as if you are fluttering down,and go running off into the street.