Final answer:
The newspaper headline implies that Russia mobilized its forces and that many nations were threatened by the coming conflict, leading to World War I. The statements about Serbia declaring war on Austria, Germany being the only nation to stop the conflict, and the imminent involvement of the United States are not supported.
Step-by-step explanation:
Based on the historical context provided, we can discern which statements are supported by the implied newspaper headline regarding the onset of World War I. Austro-Hungary's decision to declare war on Serbia after the assassination of Archduke Franz Ferdinand, followed by Russia's mobilization to defend Serbia, marked the beginning of a major conflict that rapidly expanded due to the network of alliances between major powers. Germany played a pivotal role in escalating the situation, not only backing Austria-Hungary but also having its own motives for entering the conflict. The United States, however, was initially debating its role in the conflict and did not immediately enter the war.
The supported statements would be:
- Russia had mobilized its forces.
- Many nations were threatened by the coming conflict.
Germany was not the only nation that could stop the conflict, as other great powers were involved, and it's unclear from the available information whether Serbia declared war on Austria or vice versa. The United States' involvement came later in the war; hence, the headline does not directly support that the United States would likely be drawn into war at that early stage.