Due to the failure to pay the price of construction materials at a value of RMB 3 million yuan by Singen Construction Co, City Materials Co applied to the local people’s court to declare for its bankruptcy. The court approved the application after necessary review of the facts. At the end of the liquidation process, the liquidation committee listed the assets, debts and the various expenses of Singen Construction Co as follows. (i) It had total assets of RMB 19 million yuan. (ii) It had total debts and other liabilities in the amount of RMB 29 million yuan, including: (1) wages and insurance premiums payable of RMB 3·5 million yuan (2) VAT due of RMB 3·2 million yuan (3) the expenses of liquidation of RMB 300,000 yuan (4) the various debts due of RMB 22 million yuan. (iii) Among the bankruptcy assets, Singen Construction Co held five buildings which were duly registered with the local Registry Centre of Real Estate. The Certificate of Real Estate indicated that Buildings No. 1, 2 and 3 had been detained by the order of the local court for a dispute with a third party before the liquidation process started. However, Singen Construction Co had put these three buildings as things mortgaged to Steel Company for the debts payable at RMB 2 million yuan, without registration of the mortgage agreement with the Registration Centre of Real Estate. The current assessed price of the three buildings was RMB 2 million yuan. (iv) Buildings No. 4 and 5 had been mortgaged to Financial Company for a loan of RMB 3 million yuan and been duly registered with the Registry Centre of Real Estate. The current assessed price of the two buildings was RMB 2 million yuan. Required: Answer the following questions in accordance with the relevant provisions of the Enterprise Bankruptcy Law and the Property Law of China, and give your reasons for your answer:

(a) state how to deal with the mortgage agreement between Singen Construction Co and Steel Company and the order of priority for Steel Company in allocation of the insolvent assets; (3 marks)

二冲程柴油机换气过程所占曲轴转角一般为（）。

A．130°～150°

B．100°～120°

C．150°～180°

D．110°～130°