Persia? it was known for its fertile crescent where humanity's first crops were grown
Buildings Buildings Buildings Buildings
Answer: D
Explanation: The Caravel - it was a ship designed by the Purtuguese to sail sea's.
Through my research I found questions similar to this with matching option choices, and they are the following:
A) mixed interval
B) variable interval
C) rotating interval
D) variable ratio
The best answer among the following choices would be B) Variable interval, so this would be the answer to fill in the blank.
Answer:1 is the first one, the second one is metal tools and the third one is grains and timber
Explanation: