情态动词用法
she could have worked
it could have worked
we could have worked
they could have worked
1.3 进行式型 (Continuous)：表示现在或将来还在进行的状态 I could be working (动词是be + v-ing 现在分词。下同)
you could be working
he could be working
she could be working
it could be working
we could be working
they could be working
1.4 完成进行式型 (Perfect Continuous)：表示过去正在进行的状态 I could have been working (动词是 have been + v-ing 现在分词。下同)
you could have been working
he could have been working
she could have been working
it could have been working
we could have been working
they could have been working
二、情态动词的疑问句：