What are the Reasons for a denied us citizenship?

To get US citizenship there are mainly following requirements:

1.should be 18 years old

2.should have green card

3.must have been green card holder for minimum 5 years period with continuous physical residency in US

Also you should be resident of the area from which you are submitting your application for a minimum period of 3 months.

If you fail to qualify under any one of the above main requirements you would be denied US citizenship.