4. the hindenberg disaster, a total of 36 fatalities (changed public opinion on airships forever) as well as the competition with airplanes.
5. airships and blimps are both dirigibles. a blimp (technically a “pressure airship”) is a powered, steerable, lighter-than-air vehicle whose shape is maintained by the pressure of the gases within its envelope.
6. most blimps are used as advertising devices, you will see them overhead at games played in open-air sports stadiums.
Answer: The answer is D
D because they had many scarce materials so they had to shift the process to war needs.
Answer: The Demographic Yearbook.
Explanation: Demographic Yearbook contains the collection of the official statistics about a variety of topics having a large range. They usually contain the knowledge about the status of the birth, death, population ,etc on yearly basis. They also represent the issues that arise according to the statistic such as education activity,economic rate,mortality rates, etc.This statistics has been collected from the United Nations .