答案：
小题1:Don’t bother yourself about cloning my pet cat. I won’t expect to bring it back to life.
小题2:It occurred to her that she left her key at home.
小题3:My house is nowhere near the center of the city, but it has no air pollution or traffic jams.
小题4:It was long before I realized my mistake.
小题5:If only I had followed the doctor’s advice earlier.
题目分析：
小题1:这里注意时态第一句为祈使句，第二句用的是将来时，故用Don’t bother yourself about cloning my pet cat. I won’t expect to bring it back to life.
小题2:这里it作形式主语，that引导的真正的主语，故用It occurred to her that she left her key at home.
小题3:这里应注意连词的使用，although与but只能用一个，故用My house is nowhere near the center of the city, but it has no air pollution or traffic jams.
小题4:这里是固定句式it+ be+ 时间段that，故用It was long before I realized my mistake.
小题5:这里是if only 后跟虚拟语气，对过去的虚拟用过去完成时，故用If only I had followed the doctor’s advice earlier。
点评：文中考查了固定句式，动词短语及动词时态等的用法及意义，需要考生有扎实的基础知识并能正确理解短文的内容，还需要会分析复杂的句子结构进而判断用该词的什么形