Answer & explanation
Correct answer: option 4
$\Delta I_E = \Delta I_C + \Delta I_B = 1 mA$
$\Rightarrow \Delta I_B = 0.01 mA$
$\Rightarrow \text{Current Gain for common base configuration is }\alpha = \frac{\Delta I_C}{\Delta I_E} = 0.990$
Correct answer: option 4
$\Delta I_E = \Delta I_C + \Delta I_B = 1 mA$
$\Rightarrow \Delta I_B = 0.01 mA$
$\Rightarrow \text{Current Gain for common base configuration is }\alpha = \frac{\Delta I_C}{\Delta I_E} = 0.990$