The loading, unloading, transshipment and transit of inward and outward mail bags are （） Customs control and a covering way bill should be submitted to the Customs by the enterprise providing postal service.

A. subject to

B. upon

C. into

D. with

承兑行为是指（ ）付款人承诺在票据到期日支付票据金额并盖章的行为。

A．银行汇票

B．银行本票

C．商业汇票

D．支票