Shareholders' liability when in a liquidation

Hi Mike,
I just found that the answer for the below question in OpenTuition mock exam is different from that in OpenTution Note practice questions. This is for F4 ENG variant.

Can you advise me the correct answer & explanation?

1. In a liquidation, the holder of partly paid shares will have to pay the amount as yet unpaid on those shares.. To whom is that money payable?
a. the Court
b. the liquidator
c. the company
d. the bank

Thanks a lot