have的过去式和过去分词都是 had 有 ；持有；占有；由…组成；显示出，带有(性质、特征)；
have的第三人称单数： has现在分词： having过去式： had过去分词： had
A new system has been devised to control traffic in the city.
控制城市交通的新系统已经设计出来。
I think you have made an error in calculating the total.
我想你在计算总数时出了差错。
No new SARS cases have been reported in the region.
该区没有新增非典型肺炎病例。
I've had to put my plans into cold storage.
我不得不把我的计划暂时搁置起来。
温馨提示：
