8. The eccentricity of hyperbola $C_1$ is $e_1$. Both the semi-major axis $a$ and semi-minor axis $b$ (where $a \neq b$) are increased by $m$ units (where $m > 0$) to obtain hyperbola $C_2$ with eccentricity $e_2$. Then\\
A. For any $a, b$, we have $e_1 > e_2$\\
B. When $a > b$, $e_1 > e_2$; when $a < b$, $e_1 < e_2$\\
C. For any $a, b$, we have $e_1 < e_2$\\
D. When $a > b$, $e_1 < e_2$; when $a < b$, $e_1 > e_2$