In the ancient world, why did civilizations flourish around great river valleys?
(a) river valleys protected citizens from natural disasters.
(b) river valleys provided an ideal environment for agriculture.
(c) river valleys sheltered citizens from harsh weather.
(d) river valleys contained vast mineral resources.

Correct answer choice is :

River Valley is a plan area found within the Central Area of the Central Region of Singapore. The planning area parts boundaries with Orchard in the north, Museum in the east, Tanglin in the west and Singapore River in the south. The river valleys were significant to Ancient Mesopotamia. Good farming situations made it easy to feed large numbers of people. The rivers that were close by served give a good watering source. Finally, the cities had to make a government.

explanation: the line "to save the day, harry must get past a scary three-headed guard dog" from the summary best justifies the conclusion that harry potter and the sorcerer’s stone was influenced by ancient greek mythological literature. the three other choices had nothing to do with ancient greek literature - and the words "three-headed guard dog" are what makes that choice the correct answer.