Final answer:
Option (A) Agriculture surpassed mining and became the leading industry of the California economy into the twentieth century following industrialization and advancements in farming methods.
Step-by-step explanation:
The industry that surpassed mining in 1879 and became the leading element of the California economy into the twentieth century was Agriculture. Mining initially led to rapid growth in the West, especially after major discoveries like the 1849 California Gold Rush and the Comstock Lode.
However, as the Industrialization process advanced, agriculture gained prominence with the expansion of railroads and introduction of better farm equipment, making large-scale farming more profitable and efficient.
This shift in focus from mining to agriculture marked a pivotal change in the Californian and American economy from primarily mining-based to a more diverse economy with a stronger agricultural sector.