Can someone help with Q14 that`s in the attachment. Thank you.

@ ashmeet 
i can tell you how to approach such kind of questions , 
in this perticular case u have to apply KVL . 
let v =0 
then by applying kvl we get 
12-9/2 +24-q/4 =0 
=36-3q/4=0 
now as per the formula (Q=CV )
V = Q/C 
SO, FOR 2 MICROFARAD = V = 24 V 
FOR 4 MICROFARAD = V = 12V 
SO, WHEN U CALCULATE V(A) – V(B) = 24-12 = 12V 
the option that u have given , in that both c and d options are same . 
so, both of them will be thecorrect answer . 
HOPE IT CLEARS YOUR DOUBT 
ALL THE BEST