I would believe B is the answer because it is hinting that Johnny should be doing his homework, but instead he is outside playing.
The difference between the words swarmed and assembled should give you a clue as to what the answer is. Swarmed means to move somewhere in large numbers, usually crowding around something of interest to get a closer look. Assembled means to gather together in one place for a particular reason. This is usually done in an orderly fashion.
This leads her to believe that Darcy must have a personal reason for this visit; namely, that he is in love with Elizabeth (answer: C.)
