Which of the following sentences is right?

1. A.
   Dressed as a girl, we didn't recognize him at first sight．
2. B.
   Being ill, I had to stay at home to look after my mother．
3. C.
   There stood a mass of people on each side of the street, all waving to the visiting president．
4. D.
   There were so many people waiting in the room, I had to step out．