What is $1$ billion in the Indian number system?
 

The correct option is (C),

$1$ billion is equal to $1000$ million.
We know that $1$ million is equal to $10$ lakhs in the Indian number system.
So $10$ million will be $1$ crore.
$100$ million will be $10$ crores.
And $1000$ million will be $100$ crores.
Therefore, $1$ billion will be $100$ crores in the Indian number system.