first of all.. dont think ur doubt is stupid.. ok. we all are learners and i feel no doubt is stupid.. it ensures that we are on correct path..
now coming to ur point.. why is distance getting decreased? in (A) we have to see the field due to "B".. and by superposition principle... the field due to B remains unchanged....only the" net "electeic field will chage due to decreasing distance of Q from charge A
and in part (A) we have to see the field" only" due to charge at B
@Ananya_Singh and if you are asking for charge at A.. then yes.. the field due to charge initiall at A will "increase" and that too after a finite time interval.. when the charge comes to new point
is it clear now?