For BitTorrent, which of the following is true:

A. Among the chunks that a peer does not have, the peer will request chunks that appear to be relatively rare in the torrent.
B. Although a peer may have 50 concurrent TCP connections with other peers, at any given instant of time it sends data to less than 10 other peers.
C. At a given instant of time, a peer A may upload to a peer B, even if peer B is not sending anything to A.
D. All of the above