句型转换。

1. Mr. Li began to teach English in this school in 1999. (同义句转换)

    Mr. Li _______ ________ English in this school since 1999.

2. Our monitor has been a League member for two years. (同义句转换)

   Our monitor ________ the League two years ago.

3. My grandpa had to collect water from the village well. (改为反意疑问句)

   My grandpa had to collect water from the village well, _______ ________?

4. They can hardly believe it. (改为反意疑问句)

    They can hardly believe it, _______ _______?

5. He spent hours cleaning out the refrigerator. (同义句转换)

   He _______ hours _______ _______ out the refrigerator.

变压器的纵联差动保护应符合（）要求：

A.应能躲过励磁涌流和外部短路产生的不平衡电流。

B.应能躲过变压器变二侧短路电流。

C.应具有电流回路断线和判别功能，并应能选择报警或允许差动保护动作跳闸。

D.差动保护的保护范围应包括变压器套管及其引出线，如不能包括引出线时，应采取快速切除故障的辅助措施。但在110kV电压等级的终端变电站和分支变电站，以及具有旁路母线的变电站在变压器退出工作由旁路断路器代替时，纵联差动保护可短时利用变压器套管电流互感器，此时套管和引线故障可由后备保护动作切除；如电网安全稳定运行有要求时，应将纵联差动保护切至旁路断路器的电流互感器。

E.应延时动作于断开变压器的各侧断路器。