6. In a football tournament, only 4 teams participate, called A, B, C, D. In each round, each team plays one match, and during the tournament, each team meets every other team exactly once. After the first two rounds, team A has scored 4 goals without conceding any, team B has conceded 7 goals without scoring any, team C has scored 3 goals and conceded 1, and team D has scored 1 goal without conceding any. Considering that each team earns 3 points for each win, 1 point for each draw, and no points for a loss, indicate how many points, respectively, teams A, B, C, D (in this order) have earned in the first two rounds.
(A) $4,0,3,4$
(B) $4,0,4,2$
(C) $4,0,3,2$
(D) $4,1,3,2$
(E) $3,1,4,2$
Problem 6. The answer is (A).

Team $B$ has conceded 7 goals, and must have therefore played necessarily against teams $A$ and $C$, conceding 4 goals from team $A$ and 3 from $C$, without scoring any. In the matchday when $A-B$ was played, $C-D$ was also played, while at the same time as $B-C$, $A-D$ was played. It is now easy to calculate the result of each match:

$$
A-B: 4-0 \quad C-D: 0-1 \quad B-C: 0-3 \quad D-A: 0-0
$$

The standings are therefore: 4 points for $A$ and $D$, 3 points for $C$, 0 points for $B$, corresponding to the answer $4,0,3,4$. (Problem proposed by S. Pelizzola)