19. There are at least three people in the room. At most two people in the room recognize each other. At least one person in the room recognizes everybody else in the room.
Which one of the following is not consistent with the above?
(a) Four people are in the room
(b) No two people in the room recognize each other.
(c) At most one person in the room recognizes everybody else in the room.
(d) Anyone in the room who recognizes any other person in the room is also recognized by that person..
(e) Two people in the room recognize every one else in the room.

不是很明白：（
请高手指点，谢谢！