Scout and Jem are attacked by Bob Ewell. This is Bob's revenge for Atticus defending Tom Robinson and showing Bob to be a liar in court. Fortunately for the children, Arthur 'Boo' Radley shadows them and intervenes when Bob attacks, killing him in the process.
It wouldn't really make sense to say he is lazy because the passage says, 'He must've tried it a hundred times.' Which means he put effort in and was simply unsuccessful. There is nothing malevolent about Gregor in the message, so cruel is out. You could say he was hardworking, but since he isn't doing anything but laying in bed at the moment, it doesn't make sense to put that as the answer either, hence through process of elimination, you can assume that he's simply unmotivated as he expresses mild discouragement and disinterest.
