19. In a tournament using a double round-robin format, a win earns 3 points, a draw earns 1 point, and a loss earns 0 points. It is known that six teams participated, and at the end of the tournament, the top three teams had the same score. What is the maximum score these three teams could have? 
(A) 22
(B) 23
(C) 24
(D) 26
(E) 30
19. C.

Let the teams that come in the top three be $A$, $B$, and $C$, and the other three teams be $D$, $E$, and $F$. Then, each of $A$, $B$, and $C$ should win against $D$, $E$, and $F$, meaning they should earn $3 \times 2 = 6$ points from each of $D$, $E$, and $F$, totaling 18 points.

For the matches between $A$, $B$, and $C$, to ensure that these three teams have the same score, there are two scenarios:
(1) One team draws with the other two teams, thus earning $(1+1) \times 2 = 4$ points from the other two teams, making the total score $18 + 4 = 22$.
(2) One team wins one match and loses one match against the other teams, thus earning 3 points from each of the other teams, totaling 6 points, making the total score $18 + 6 = 24$.
Therefore, the highest score that meets the requirements of the problem is 24 points.