sandwich structure construction

例句：

1. 1. She ate a delicious sandwich for lunch.
   她吃了一顿美味的三明治午餐。
2. 2. The sandwich was so good that I couldn't stop eating it.
   这个三明治太好吃了，我根本停不下来。
3. 3. They served sandwiches as an appetizer before the main course.
   在主菜之前，他们提供三明治作为开胃菜。