听力原文： A bill of exchange is a negotiable security signed and dated by the issuer ( the drawer). It contains an unconditional order or instruction for the debtor ( the drawee) to pay a fixed sum of money to a certain person or to his order upon maturity. If the debtor agrees to this, he accepts the bill of exchange by signing it. Its form, content and legal consequences are regulated by law. A promissory note only differs from a bill of exchange in that it is issued in the form. of a promise of payment made by the debtor instead of a payment order or instruction by the creditor. 28. Who signs and dates a bill of exchange? 29.What is a bill of exchange? 30.Which of the followings regulates the form, content and legal consequences of the bill of exchange? (28)