There are five friends sitting in a row. Let's represent the positions as ____.
Information given:
Let's combine these pieces of information:
Case 1: D is at the leftmost end.
D ____
Since B is between D and E, the sequence must start D B E:
D B E ____
The remaining two positions must be filled by the pair (A C).
So, the arrangement is: D B E A C.
Let's check if this is consistent with condition 1 (A C together): Yes.
Positions:
In this arrangement, the person in the middle (3rd position) is E.
Case 2: D is at the rightmost end.
____D
Since B is between D and E, the sequence must end E B D (reading from left to right):
__ ___E B D
The remaining two positions must be filled by the pair (A C).
So, the arrangement is: A C E B D. Positions:
In this arrangement, the person in the middle (3rd position) is E. In both valid arrangements, E is in the middle.
\[ \boxed{\text{E}} \]
Four teams – Red (R), Blue (B), Green (G), and Yellow (Y) – are competing in the final four rounds of the Inter-School Science Olympiad, labeled Round A, Round B, Round C, and Round D. Each round consists of one match between two teams, and every team plays exactly two matches. No team plays the same opponent more than once.
The final schedule must adhere to the following rules:
(193 words)