Discoveries made in California more than doubled the world's supply of which item?
A. gold
B. farmland
C. oil
D. water

The correct answer is letter A

On the morning of January 24, 1848, carpenter James Wilson Marshall and his staff worked on the construction of a sawmill at John Sutter's ranch in the Sierra Nevada region of central California. Marshall had to bypass a stream to install the saw, moved by the force of the water. When he looked at the muddy bed of the Americans' river, something caught his eye: there was something shining there in the sunlight. It was gold.

The gold that flowed in California was generous. In the first months after the discovery, it was possible to collect the nuggets directly from the soil. Just crouch and pick it up. The precious metal was found in riverbeds and in ravines that flow. Mexican Antonio Franco Coronel, for example, left the job of teaching in Los Angeles and in three days of mining collected 4.2 kg of gold.

the first question's answer is a.