GOLD . . . NEAR SAN FRANCISCO IN 1848, AND THE GOLD RUSH STARTED TH...

6. - BAI KIEM TRA 1 TIET LAN 1
BAI KIEM TRA 1 TIET LAN 1
6. Gold . . . near San Francisco in 1848, and the gold rush started the following year.a. discovered b. was discovered c. has been discovering d. is discovering