A、In 1848. B、In 1846. C、In 1884. D、In 184 A信息明示题。文章开头就指出，淘金热始于1848年，故选A。

In 1848, gold was discovered near San Francisco, and the first great gold-rush began. When the news spread, farmers, lawyers, sailors, soldiers and school teachers rushed to California by what ever means they could. Within a year, 100,000 people only 8,000 of whom were Women had reached the coast of California. More than half of them had traveled overland across the American continent. "Gold fever" began to spread. Settlements throughout the United States were deserted. Homes, farms and stores were abandoned as everybody raced for California. Many came by sea, and in July 1850 more than 500 ships were anchored in San Francisco Bay, many of which had been deserted by gold- hungry sailors. A few people became very rich, but it was a risky business. Law and order broke down. Even if a miner "struck it rich", there were always those who would try to take it away: gamblers, outlaws, and thieves. Gold and silver were discovered in Nevada a few years later, and "gold fever" was an important part of the colonization of the western United States.