When the triode operating in the linear region, it indirectly

implies that the grid voltage, plate voltage and plate current is

specified and hence plays no contribution to the amplification factor in this question

Now if the grid is too near the cathode it will partially or completely lie in space charge region which comprises of electrons from the cathode. And hence it will pick electrons from cathode more rapidly which will increase the plate current and hence amplification factor will get affected. As amplification factors depend on the plate’s current.

And when the grid is far away from cathode, it will able to pick as many electrons compared to when it was near to cathode and hence amplification factor will get affected