A、Gold was discovered in the city. B、The city’s population grew to twelve thousand. C、The Golden Gate Bridge was constructed. D、

From this lookout we enjoy one of the most spectacular views of San Francisco. As you can see, the city rests on a series of hills varying in altitude from sea level to 938 feet, The first permanent settlement was made at this site in 1776. For thirteen years the village had fewer than 100 inhabitants.[20]But in 1848, with the discovery of gold, the population grew to ten thousand. The same year the name was changed from Yerba Buea to San Francisco. By 1862 telegraph communications linked San Francisco with eastern cities, and by 1869, the first transcontinental railroad connected the Pacific coast with the Atlantic seaboard.[21]Today San Francisco has a population of almost 3 million. It is the financial center of the west, and serves as the terminal for trans-Pacific steamship lines and air traffic. The port of San Francisco which is almost 18 miles long with 42 wharves, handles between 5 and 6 million tons of cargo annually. And now, if you look to your right, you should just be able to see the east section of the Golden Gate Bridge. The bridge, which is more than one mile long, spans the harbor from San Francisco to Marin County and the Red Wood Highway.[22]It was completed in 1937 at a cost of 32 million dollars and is still one of the largest suspension bridges in the world.
20. According to the speaker, what happened in 1848?
21. What is the population of San Francisco now?
22. What can we learn about the Golden Gate Bridge?