To answer this question, we need to understand the history of zero.
The concept of zero as a numerical digit was invented by ancient Indian mathematicians. The earliest recorded use of zero as a number and a placeholder in a positional numeral system can be traced back to the Indian mathematician Brahmagupta in the 7th century. This invention of zero was a significant development in mathematics and had a profound impact on various fields, including arithmetic, algebra, and calculus.
Therefore, the correct answer is:
A) India - This option is correct because ancient Indian mathematicians invented the concept of zero as a numerical digit.