The US role played in the Vietnam War was C. The US became involved because they feared that other countries would fall to communism like dominoes. The Vietnam War was the longest war fought by the US in its history until the War in Afghanistan surpassed it recently. Involvement began slowly at first but gradually ramped up resulting in a widespread feeling of war weariness in the US where activists began to actively oppose war efforts and speak out against involvement on the whole.
It decreased prices for consumers.
That is because the Czar knew that fighting the Austria-Hungary empire and Germany was inevitable and war was brewing. Of course, Russians did not see the end of the war due to the Bolshevik revolution that had them retreat from the war and cease their participation and overthrowing the king.
The French Revolution Hope This Helps!