Final answer:
The most credible source concerning the rumors of the gold discovery in California would be government announcements.
Step-by-step explanation:
The most credible source concerning the rumors of the gold discovery in California would be government announcements. Government announcements are considered credible because they are official statements made by a recognized authority. In this case, the government would have had access to accurate information and would be able to provide the public with reliable updates on the gold discovery.
Newspaper reports, letters from gold miners, and oral accounts from travelers could also provide valuable information, but they may be less reliable as they are subjective and may contain biases or inaccuracies. However, they could still be used as supplemental sources to gain a broader understanding of the gold discovery.