题目

The first big wave of Chinese immigration to America came when gold was discovered in California in 1848.The Chinese called the new land“Mountain of Gold”．Those who did not become miners found work in railroad construction，farming and light industries，doing low paid jobs.By the 1880s，American industrialization brought changing economic realities，resulting in an explosion of resentment (仇恨) toward the Chinese laborers.They were accused of taking jobs away from the white men.The government issued Exclusion Acts(《排外法案》)to stop the immigration of Chinese labore（2005•漳州）如图，一铁路路基的横截面是等腰梯形，∠B=∠C=45°，根据图中数据计算路基的高为    m．