Look at the four squares [■] that show where the following sentence could be inserted in the passage. Such periods of freezing would probably prevent life from developing. Where could the sentence best be added? Click on a square [■] to insert the sentence in the passage.
A. Square A.
B. Square B.
C. Square C.
D. Square D.
【C13】
A. since
B. once
C. when
D. while
The word it in the passage refers to
A. ice
B. soil
C. moon
D. solar system
All of the following are cited as reasons why civilizations developed EXCEPT
A. Religious practices unified the population.
B. The management of water required organization.
C. A major climate change made living in groups necessary.
D. Extra food resulted in the expansion of population centers.