11. The discussion_____ alive when an interesting topic was brought in.
A. was coming         B. had come         C. has come     D. came
12. Happy birthday, Alice! So you have ____ twenty-one already!
A. become         B. turned             C. grown       D. passed
13. Why don't you put the meat in the fridge? It will ______ fresh for several days.  
A. be stayed B. stay 　　 C. be staying D. have stayed
11. D。come alive是系表结构，表示“变得活跃起来”。
12. B。turn在这里的意思是：(指时刻、年龄)超过，逾。
13. B。stay fresh是系表结构，表示“保持新鲜”，因此没有被动语态和进行时。