By the end of next year,they will have finished work on the new stadium.work前为什么不加the

题目

By the end of next year,they will have finished work on the new stadium.work前为什么不加the
Work on it had begun before my sister left.这幢房子是在我姐姐离开前动工的.(23课)
By the end of next year,they will have finished work on the new stadium.到明年年底他们将完成新体育场的工程.(37课)
为什么不是 the work,

答案

after work 没有the
可加可不加,work是抽象的工作