The correct answer is A. 12.30%.
As per the census 2011, the percentage of population of children (0-6 year) in Haryana is 12.30%. This means that out of every 100 people in Haryana, 12.3 are children below the age of 6.
The other options are incorrect. Option B is 13.30%, which is higher than the actual percentage. Option C is 13.60%, which is also higher than the actual percentage. Option D is 13.90%, which is the highest of all the options and is also higher than the actual percentage.
The percentage of population of children (0-6 year) in Haryana has been declining over the years. In the census 2001, this percentage was 14.20%. This decline is due to a number of factors, including a decline in fertility rates, an increase in the average age of marriage, and an increase in the number of women in the workforce.