题目

这句话为什么用过去时
新目标9年级第十四单元的一篇文章,He's already visited the place where his ancestores lived.通篇都用的现在完成时和一般现在时（只有讲到“祖先”们怎样怎样时才用一般过去时）,可在倒数第二段插了一句一般过去时,而且不是讲“祖先”的,我很不理解,整篇文章如下：
Have you been back to the place where your ancestors lived,worked,studied and played?Robert Qian,a Chinese Canadian,already has.Now in China,he has found that his family is like a tall tree with long roots.
Robert is just one young overseas Chinese who has come to visit his ancestors' homeland,as part of the In Search of Roots summer camp program.The program is organized by the local government of Guangdong Province.This program started in 1980,and so far has brought thousands of overseas Chinese students to China to look for their families' roots.The young people are usually between 16 and 25 years old.Most,like Robert,can hardly speak any Chinese,and have never been to China before.
The students mainly visit parts of Guangdong Province in southern China.During the two-week camp,they study Chinese culture,see changes that have happened in that area,and visit interesting sights.Going to their ancestors' village is often the most exciting part of the trip.The students feel that they are part of the village,and experience village life.They drink from the village well,go for walks through the countryside,and watch the villagers do their daily activities.
Cathy Qin,a young American student,had（我说的就是这个过去式had） this to say,"Thanks to In Search of Roots,I am beginning to understand my Chinese roots,and who I am.It has been a great trip,and I have so many memories of China to take with me."
The program leaders believe strongly in the program and say that the purpose of it is to give young overseas Chinese the chance to learn more about themselves."I've really enjoyed the trip so far," says Robert."This has been a big step for me,and I'm looking foreard to finding out more about my roots during my time here."

提问时间：2021-01-02

答案

整篇文章是对这个In Search of Roots summer camp program夏令营活动内容的介绍,所以用一般现在时表陈述.引用那个学生的话是一个过去发生的事情,所以用一般过去式.这种文体在新闻类和宣传类文章里比较常见,见多了就熟悉了.