3. For all $m, n$ satisfying $1 \leqslant n \leqslant m \leqslant 5$, the number of different hyperbolas represented by the polar equation $\rho=\frac{1}{1-c_{m}^{n} \cos \theta}$ is
A. 15
B. 10
C. 7
D. 6
3. $\mathrm{D}$ Hint: $C_{m}^{n}>1$, remove the repeated cases only.



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