非延续性动词转化为延续性动词

怎样将非延续性动词转化为延续性动词？老师上课好像讲的是改为 be in？什么意思啊？谢谢

延续性动词说的是，这个动作可以延续一段时间，比如中文的睡觉，吃饭，学习等，可以持续一段时间
非延续性动词就是说这个动作不可以延续一段时间，比如，还钱，眨眼睛，死亡等，这个动作不能够持续一段时间，因为买东西是交钱一瞬间的动作，死也是一瞬间的动作，因此不能和段时间连用。
延续性动词与非延续性动词之间的转换：

leave → be away离开;borrow → keep借;buy → have买;begin/start → be on开始/上演;die → be dead;finish ／end ／stop→ be over结束/完成;join → be in+组织机构或be a member of+组织机构；open/close sth → keep sth open/closed；fall ill → be ill；get up → be up；catch ／get a cold → have a cold感冒；come here → be here；go there → be there；become → be成为；come back → be back；fall asleep → be asleep睡着；get to/ arrive/reach → be (in)；leave → be away from；get to know → know；go (get) out → be out；put on → wear；catch a cold →have a cold; go to school → be in school／be a student上学; go abroad → be abroad去国外; marry → be married（to）结婚; wake up → be awake 醒; make friends with → be friends with成为/交朋友; lose → be lost ／be missing ／be gone 丢失; lose one's job ／work → be out of work ／a job等。
请看例句1.The old man died 4 years ago.
→ The old man has been dead for 4 years. → It is 4 years since the old man died.
→ Four years has passed since the old man died.