for prospects of promotion 为晋升的前途

for higher responsibility 为更高层次的工作责任

for wider experience 为扩大工作经验

due to close-down of company 由于公司倒闭

due to expiry of employment 由于雇用期满

offered a more challenging opportunity 获得的更有挑战性的工作机会

sought a better job 找到了更好的工作

to look for a more challenging opportunity 找一个更有挑战性的工作机会

to seek a better job 找一份更好的工作