9. The real semi-major axis length a and imaginary semi-minor axis length $\mathrm { b }$ of a hyperbola $C _ { 1 }$ with eccentricity $e _ { 1 }$ (where $a = b$) are both increased by $\mathrm { m } ( m > 0 )$ units of length to obtain a hyperbola $C _ { 2 }$ with eccentricity $e _ { 2 }$. Then A. For any $\mathrm { a } , \mathrm { b }$, $e _ { 1 } < e _ { 2 }$ B. When $a > b$, $e _ { 1 } < e _ { 2 }$ ; when $a < b$, $e _ { 1 } > e _ { 2 }$ C. For any a, b, $e _ { 1 } > e _ { 2 }$ D. When $a > b$, $e _ { 1 } > e _ { 2 }$ ; when $a < b$, $e _ { 1 } < e _ { 2 }$
9. The real semi-major axis length a and imaginary semi-minor axis length $\mathrm { b }$ of a hyperbola $C _ { 1 }$ with eccentricity $e _ { 1 }$ (where $a = b$) are both increased by $\mathrm { m } ( m > 0 )$ units of length to obtain a hyperbola $C _ { 2 }$ with eccentricity $e _ { 2 }$. Then
A. For any $\mathrm { a } , \mathrm { b }$, $e _ { 1 } < e _ { 2 }$
B. When $a > b$, $e _ { 1 } < e _ { 2 }$ ; when $a < b$, $e _ { 1 } > e _ { 2 }$
C. For any a, b, $e _ { 1 } > e _ { 2 }$
D. When $a > b$, $e _ { 1 } > e _ { 2 }$ ; when $a < b$, $e _ { 1 } < e _ { 2 }$