Key idea: This is a "Guaranteeing Qualification" question, recognisable because it asks for the minimum points to ensure advancement regardless of other results. The method involves constructing the worst-case scenario where the top teams maximize their points, while accounting for the hidden constraint that the bottom teams must play each other.
Step 1: Calculate the total points in the tournament.
Number of teams N=8.
Total matches = (28)=28.
In a 2-1-0 system, every match awards exactly 2 points in total.
Total points in the tournament = 28×2=56.
Step 2: Construct the worst-case scenario for the top 5 teams.
To find the maximum possible score for the 5th place team (the highest score that fails to qualify), we must minimize the points of the bottom 3 teams.
The bottom 3 teams play (23)=3 matches among themselves.
Regardless of the outcomes, these 3 matches will generate exactly 3×2=6 points for the bottom 3 teams.
They can get 0 points from matches against the top 5 teams (by losing all of them).
Thus, the minimum possible total points for the bottom 3 teams is exactly 6.
Step 3: Calculate the maximum points available for the top 5 teams.
Maximum points for top 5 = Total points - Minimum points for bottom 3
Maximum points for top 5 = 56−6=50.
Step 4: Find the maximum score for the 5th place team.
If the top 5 teams share the 50 points as equally as possible, their average score is 50/5=10.
It is possible for all 5 teams to score exactly 10 points. In this case, the 5th place team has 10 points and is eliminated (due to tie-breakers).
Therefore, 10 points does NOT guarantee qualification.
Step 5: Determine the guaranteeing score.
If a team scores 11 points, can 4 other teams also score 11 or more?
The sum of the top 5 teams would need to be at least 5×11=55.
However, the maximum available points for the top 5 teams is 50.
It is impossible for 5 teams to score 55 points. Thus, at most 4 teams can score 11 or more points.
A team with 11 points is guaranteed to be in the top 4.
Answer: C