It's b, because a mixed economy refers to socialism, where they have some control over economic decisions, but not all.
Indus Valley Civilization would not have developed or sustained for long time without the Indus River. The Indus River helped the creation of Indus Valley Civilization which can be seen through the nomenclature of the Civilization.
The Indus River provided the people with water for cleaning and drinking and thus contributed in Civilization's health and hygiene as well as drainage system, the latter being one of the important characteristics of this Civilization.
The people had to rely on Indus River for irrigation of their crops which lead more cultivation and increased surplus.
The Indus River was used by the people to transport their goods and for trade relations with contemporary Civilizations of Egypt and Mesopotamia.
The people also relied on Indus River for sustenance of animals used by them.
All the above things which were possible due to Indus River helped in the Creation and development of Indus Civilization.
I would say the last three
