当前，能源问题已引起世界各国的高度重视，21世纪核能将成为世界的主要能源之一．我国现已成为第二能源消耗大国，并正在大力开发利用核能，那么，在世界和平利用核能的过程中，人类利用的是原子核____变时释放的能量．

Last year my father ______ the city where he was born.

    John was a kind man. When he was young, he hoped ____(become) a singer. But he didn't have enough money ____ (buy) books about music. And his parents didn't expect him ____ (be) a singer. So his dream didn't come tree. At the age of fifteen, he ____ (leave) his village and found a job in a small town. He worked there for five years. Later his mother became very ill (生病的) and he had to ____ (stop) his work to come back and look after (照顾) her. Three years later his mother died and he wanted to leave his village again and  ____ (work) in other places. However, John couldn't. His father was ill. John decided____ (stay) at home and look after him. Every day he ____ (do) many things for his father. Day by day, John became old. But he still didn't forget his dream to be a singer. Now he has lots of time so he plans to learn to sing at a music school.