The Indus River Valley probably began around ​ (a)   years ago. Artifacts such as weights and scales were probably used to measure ​ (b)   and represented a standard money system in the Indus River Valley. The Great Bath was probably used in ​ (c)   rituals. More than 400 ​ (d)   have been found on stone seals, but archaeologists are unsure of what they mean. Mohenjo-daro had an advanced ​ (e)   system made of brick pipes to get rid of waste.

Sometime around 1900 b.c., the people of the Indus Valley began to ​ (a)   their cities and villages. Why did the people leave? Archaeologists have found several possible causes. There was a severe ​ (b)   that lasted for hundreds of years. It destroyed crops and caused people to starve. ​ (c)   and floods killed many more people and changed the course of the Indus River. Meanwhile, groups of people called the ​ (d)   migrated to India. Soon a new ​ (e)   emerged.

The ​ (a)   were not a race or ethnic group. Many historians believe that the Aryan people's language was part of a large language family known as Indo-European. A language family is a group of similar ​ (b)   . Many modern Indian languages, like ​ (c)   , are part of the ​ (d)   family. So are many European languages, including ​ (e)   . The Aryans were speakers of Indo-European languages.

This image shows the social classes of ancient Indian society, also known as the (a)  

Hinduism (HIHN • doo • ih • zuhm) is one of the world's ​ (a)   religions. It is also the ​ (b)   largest religion, after ​ (c)   and Islam. Hinduism has no one ​ (d)   and no one holy book. Hindus usually pay respect to the ​ (e)   . They also take part in religious rituals, either at home or in a local temple.