How much gold , arriving in San Francisco, triggered the gold rush?
a- 500 lbs
b- 1 ton
c- 2 tons
My answer is 2 tons
I wish you'd clarified this from the beginning.
You must be talking about the Klondike Gold Rush, not the California Gold Rush.
http://www.nps.gov/klgo/forkids/the-story-of-the-klondike-gold-rush-pg-1.htm