Unrestricted submarine warfare, which became prominent in World War I, meant that submarines could sink any time of vessel at any time without warning. Before this, they had to surface first and place crews on lifeboats.
Historical Cycle or sometimes a recurring theme
Generally speaking, a "mixed" economic system can be characterized by some government involvement and private ownership of most business, since some government regulation ensures the protection of the consumers.
Answer:
Sacred Books.
Explanation:
Books like the Quran, Bible, and Torah are religious books.
