Which of these are ancient indian achievements that spread to other regions of the world?
a: arabic numerals and buddhism
b: the idea of citizenship and metalworking
c: the caste system and use of coins
d: polytheism and human figures in art

C: the caste system and use of coins

Explanation:

The caste system is a particular form of social stratification to which one belongs only through birth and is characterized by having a solid, rigid and immobile system. The caste system in India describes the social stratification and social constraints present in the Indian subcontinent, where social classes (varnas or 'castes') are defined by thousands of inbred hereditary groups, often called yati or 'clan') . Within a yati there are hereditary groups called gotra, the lineage of an individual. India was one of the first territories to coin money, around the sixth century BC. It is believed that the first "rupee" was introduced by Emperor Sher Sacha Suri, and it consisted of 40 parts of copper (paise). Among the first issues of paper money include those issued by the Bank of Hindustan (1770-1832), the General Bank of Bengal and Bihar (1773-1775) and the Bank of Bengal (1784-1791), among others.