what did the Indians discover 1500 years ago? A:Pi, B: Zero, or C:E.

Hello.

B. Zero.

sources:

" By six hundred AD, the mathematician Brahmagupta in India was
clearly asserting that any number subtracted from itself was zero. He
also struggled with adding, multiplying -- even dividing by zero. At
that same time, Mayas in the western hemisphere had many symbols for
zero. They even had a god of zero -- a god of death whom they used in
some their more ghastly rituals.
India took up the use of a dot to signify zero. The concept eventually
seeped out of India. It seems to've traveled the Silk Road to the Arab
world, in the tenth century. There it mutated from a dot into a
circle. And the Arabs learned how to make it a functional part of
arithmetic and algebra."
source: University of Houston - Zero
http://www.uh.edu/engines/epi1823.htm

"Did you know that the number zero was discovered by
Hindumathematicians around the sixth century?"
"http://amos.indiana.edu/library/scripts/zero.html

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search strategy:
"zero was discovered"
zero india century site:edu

I hope this helps.

If by "indian" you mean East Indian, then the answer serves.

However, if you meant an Indian of the Americas, there is another possibility.

In his recent book "1491", Charles Mann claims that the Mayans were
using zero by the fifth century, which would put it before its use on
the Indian subcontinent.