商业银行核销呆帐贷款的程序是（）
A.先金额小后金额大
B.呆帐形成三年以后核销
C.上级要求核销
D.先认定后核销
参考答案：D
解方程：x2＋2x-15＝0.
The loading, unloading, transshipment and transit of inward and outward mail bags are subject to Customs control and a ( ) way bill should be submitted to the Customs by the enterprise providing postal service.
A．cover
B．covering
C．covered
D．having covered
