The correct option is A 400 mL
We know that, in the case of neutralisation,
Meq.of Acid = Meq. of Base
i.e. Meq.of HCl = Meq. of NaOH
∴NHCl×VmL=NNaOH×VmL
Also, N = M × n−factor
n−factor of HCl=1
n−factor of NaOH=1
Thus, NHCl=MHCl and NNaOH=MNaOH
Hence,
2×200=1× V
(Where V is the volume of NaOH in mL)
∴Volume of NaOH = 400 mL