What book did the 1st Sergeant carry during WWI?

The 1st Sergeant carried The Blue Book during WWI. This publication was significant as it served as a training manual that provided soldiers with essential information on military regulations and standards. The Blue Book was instrumental for leadership, particularly in ensuring that non-commissioned officers, like the 1st Sergeant, were well-versed in their roles, responsibilities, and the expectations placed upon them in maintaining discipline and effectiveness within the ranks.

The other book options, while they may refer to various military documents or manuals, do not specifically pertain to the historical context of what the 1st Sergeant carried during World War I.