How long was the Blue Book in use?

How long was the Blue Book in use?

• A. 85 years
• B. 50 years
• C. 100 years
• D. 25 years

Answer: (A)

Duration is measured by the time span from when the Blue Book first came into use to when it was replaced. If the correct answer is 85 years, that means the Blue Book served as the standard for 85 consecutive years before a newer reference took its place. In practical terms, you’d take the starting year and add 85 to reach the ending year it was still in use. This long span reflects its role as the authoritative guide for a substantial period before updates changed the reference material. The other values would imply start and end dates that don’t align with how long the Blue Book remained the standard.

Duration is measured by the time span from when the Blue Book first came into use to when it was replaced. If the correct answer is 85 years, that means the Blue Book served as the standard for 85 consecutive years before a newer reference took its place. In practical terms, you’d take the starting year and add 85 to reach the ending year it was still in use. This long span reflects its role as the authoritative guide for a substantial period before updates changed the reference material. The other values would imply start and end dates that don’t align with how long the Blue Book remained the standard.