参考答案：

In accordance with Article A0A of the Contract Law, the debtor may deposit the subject matter if the obligation is diffi cult to discharge under any one of the following circumstances: (i) The creditor refuses to accept the discharge of obligation by the debtor without justifi ed reasons; (ii) The creditor’s whereabouts is unknown; (iii) The creditor is deceased but the successor is not yet determined or the creditor loses capacity for conduct but a guardian is not yet determined; (iv) Other circumstances provided by law.