用所给动词的适当形式完成句子。   

1. I often ________ donuts for lunch. (eat)

2. Danny _________ sandwiches yesterday. (eat)

3. What did Miss Zhang ________ ? (say)

根据我《UCP600》的规定，信用证经修改后，开征行即不可撤销地受该修改的约束，受益人收到修改通知后，原信用证的条款失效。