At the time of forfeiture of shares, share capital account will be debited by:

Called-up amount

The correct answer is Option (4) - Called-up amount.

Forfeiture of Shares issued:

Share Capital A/c..........(Called up amount) Dr.
          To Share Forfeiture A/c...........(Paid up amount)
         To Share Allotment A/c
         To Share Calls A/c (individually)
(..... shares forfeited for non-payment of allotment money and calls made)

The above journal entry is passed on forfeiture of shares. Thus, share forfeiture account is debited with called up amount.