By the 2005 Amendment of the Hindu Succession Act, 1956, a son is liable to pay which of the following?

Section 6(4) of the Hindu Succession Act, as substituted in 2005, abolishes the pious obligation of a son, grandson or great-grandson to pay his father's debts contracted after the amendment, but its proviso preserves a creditor's right to proceed against them for debts contracted before it. Because the pious obligation never covered tainted (illegal or immoral) debts, the son remains liable only for an "Untainted debt procured by father before the amendment in the Act". An untainted debt contracted after the amendment cannot be recovered from him on the ground of pious obligation.