I got the answer correct.
1. But when I was reviewing the question I started to wonder if the resistance would decrease since R=V/I, and voltage stayed the same (according to the explanation) while the current increased.
This seems like an obvious yes, but I'm not sure since the explanation says "the only effect on the apparatus of electron ejection from the cathode is the current in the circuit."
2. If the resistance did decrease, then would that be the resistance across the photodiode?
3. Also, since the current did increase in the circuit, then wouldn't the voltage drop across the resistor increase since V=IR?
I'm not very well-versed with photoelectrics, obviously. I'm not sure if my questions even make sense.