==> In the original condition, there are 2 variables (m,n) and in order to match the number of variables to the number of equations, there must be 2 equations. Since there is 1 for con 1) and 1 for con 2), C is most likely to be the answer. By solving con 1) and con 2), from con 1), you get \(9^n=(3^2)^n=3^{2n}=3^m\), which becomes \(2n=m\). In order for con 2) to satisfy as well, you only get m=n=0, hence it is unique and sufficient. The answer is C. However, this is an integer question, one of the key questions, so you apply CMT 4 (A: if you get C too easily, consider A or B). For con 1), the way to satisfy \(9^n=(3^2)^n=3^{2n}=3^m\) to \(2n=m\) is not unique and not sufficient. For con 2), from \(2^n=5^m\), you get \(2^n=even\) and \(5^m=odd\), so even≠odd. Only m=n=0 satisfies this, hence it is unique and sufficient.

Therefore, the answer is B, not C.

Answer: B

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