What happened when newer, more accurate weapons were used agianst close order formations at antietam?

The correct answer is C). Both sides suffered huge losses.  

With more accurate weapons used against close order formations, the losses on both sides were so high that the battle was recorded as the bloodiest day of the Civil War.

The battle of Antietam was the single-most bloodiest day of the war. The Battle of Antietam was a six hours long battle during the Civil War. There were over 23,000 casualties. About 7,000 people died and the rest were wounded or missing.

The Confederates states wanted the recognition of European governments. The plan for the Confederacy was to invade Maryland so they could join the Confederacy. In the end, Robert Lee’s troops failed to inavade Maryland.