ISP 981.01 Scope and Applicationa. These Rules are intended to be applied to （） letters of credit (including performance, financial, and direct pay standby letters of credit).b. A standby letter of credit or other similar （）, however named or described, whether for domestic or international use, may be made subject to these Rules by express reference to them.c. An undertaking subject to these Rules may expressly modify or （ ） their application.d. An undertaking subject to these Rules is hereinafter referred to as a "（ ）".