CDCS问题讨论

在网上找到的CDCS EXAM EXERCISE，大家可能已经见过了。谁来解释一下啊？If it is possible, please reply in English. Thanks.
1、A documentary credit subject to UCP 500 bears a title Irrevocable Documentary Credit has a special condition as follows:
This documentary credit will become inoperative upon receipt of a cable to this effect from the issuing bank after issuance.
After receipt of such a cable advice, the beneficiary made a presentation nevertheless. The issuing bank sent a