7. 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 conceded 1 goal and scored 3, team B has scored 4 goals without conceding any, team C has scored 1 goal without conceding any, and team D has conceded 7 goals without scoring any. Considering that 3 points are awarded 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) $4,6,1,0$
(B) $4,4,2,0$
(C) $4,3,2,1$
(D) $1,6,4,0$
(E) $3,4,4,0$
Problem 7. The answer is (E).

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

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

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