A、Because Chinese laborers grew to a large number. B、Because most Chinese were different in their physical appearance and dresse

Man: In the late 1850s Chinese laborers flooded into American and it was not until early 1860’s that many more Chinese arrived in California. Was there any improvement for Chinese’s living conditions?
Woman: Oh, no. This time when the men were imported as work crews to construct the first transcontinental railroad. They were sorely needed because the work was so strenuous and dangerous, and it was carried on in such a remote part of the country the railroad company could not find other laborers for the job. As their predecessors, these Chinese were almost all males.
Man: And I guess they, too, encountered a great deal of prejudice?
Woman: Exactly. The hostility grew especially strong after the railroad project was completed, and the imported laborers returned to California—thousands of them, all out of work.
Man: And their days were even harder?
Woman: Yes. Because there were so many more of them this time, these Chinese drew even more attention than the earlier group did. They were so very different in every respect.
Man: I think so. Like their physical appearance, the long pigtail at the back of their otherwise shaved heads; the strange, non-western clothes, the speech and their religion.
Woman: What’s more, when times were hard, they were blamed for working for lower wages and taking jobs away from white men. Anti-Chinese riots broker out in several cities. Chinese were barred from using the courts and also from becoming American citizens. Finally in 1882, the Congress passes the Chinese Exclusion Act, which stopped the immigration. Many Chinese returned to their homeland, and their numbers declined sharply in the early part of this century.
Questions:
27.When did Chinese laborers arrive in California?
28.Why were so many Chinese workers needed for the work?
29.Which of the followings is NOT the reason why Chinese people were prejudiced?
30.What directly accounts for the drastic drop in Chinese immigrants according to the passage?