The current gain in a common base circuit is 0.98. When the emitter current is changed by 5 mA, then the change in collector current will be:

0.196 mA 2.45 mA 4.90 mA 5.10 mA

4.90 mA

$α=\frac{ΔI_C}{ΔI_E}$ or $ΔI_C=α\,ΔI_E=0.98×5=4.90mA$