3. (10 points) After the spring semester started, many students donated part of their New Year's money to students in poor mountainous areas. Afterwards, four students, A, B, C, and D, had the following conversation:
A: “At least one of C and D donated.”
B: “At most one of D and A donated.”
C: “At least two of you three donated.”
D: “At most two of you three donated.”
It is known that all four students are telling the truth and exactly two of them donated. Who are these two students? ( )
A. A, B
B. C, D
C. A, C
D. B, D
3. (10 points) After the spring semester started, many students donated part of their New Year's money to underprivileged students in mountainous areas; afterwards, four students, A, B, C, and D, had the following conversation:
A: “At least one of C and D donated.”
B: “At most one of D and A donated.”
C: “At least two of you three donated.”
D: “At most two of you three donated.”
It is known that all four students are telling the truth and exactly two of them donated. Who are these two students? ( )
A. A, B
B. C, D
C. A, C
D. B, D
[Analysis] Since exactly two students donated, according to:
C: “At least two of you three donated, which means the donors can only be two out of A, B, and D, and C did not donate;
A: “At least one of C and D donated” Since C did not donate, it must be D who donated;
B: “At most one of D and A donated” It can only be D, so A did not donate;
This also confirms that D: “At most two of you three donated” is correct.
Based on this, we can solve the problem.
[Answer] According to the analysis:
C: “At least two of you three donated, which means the donors can only be two out of A, B, and D, and C did not donate;
A: “At least one of C and D donated” Since C did not donate, it must be D who donated;
B: “At most one of D and A donated” It can only be D, so A did not donate; This also confirms that D: “At most two of you three donated” is correct, meaning only B and D donated. Therefore, the answer is: $D$.