Conservation and recycling were
during world war ii

The correct answer to this open question is the following.

Conservation and recycling were important during World War II.

During wartime, the federal government of the United States asked its citizens to take of food and other stuff because supplies had to be sent to the war front to replenish the troops. Indeed, the US government asked its citizens to create food gardens in their backyards to grow crops such as fruits and vegetables to have more food because it was needed. They were called Victory Gardens. This example was followed by other countries.

c or d both can be the answer