sentence fragment即句子片段是什么?

sentence fragment即句子片段,指的是不完整的句子.
从语言学上说,一个句子通常应该具有完整的意思,完整的成分,完整的语法单位等等.
sentence fragment 有残缺句子,不完整句子的意思.
例如下面几个句子,
Mrs.Blanco gone to visit her mother at the hospital.
Finding a parking space there is usually easy during the week.
Driving in the city during the evening rush hour.
My brother has been running a charter fishing boat for five years.
Many of his customers coming back three or four times over the summer.
His business been so busy that he has very little time for anything else.
其中只有第二个和第四个是完整句,其他都是句子片段.
很明显这些句子都缺少谓语.

是电脑上的把，估计就是一篇文章中的几个句子、、、