this is from a USCIS SITE SO IT OFFICIAL GUIDE TO CITIZENSHIP PROCESS WHICH I PASSED 4 YEARS AGO
* You are a lawful permanent resident (green card holder);
* You must be 18 years of age or older;
* You have resided in the US as a LPR for at least 5 years, with no single absence from the US of more than one year. Absence of more than 6 months may restart the clock of counting Continuous Residence (Note that "resided" means "retained legal residence," which is different than "physically present" in the following requirement);
* You have been physically present in the US for at least half of the last 5 years (30 months) ("physically present" means you are actually in the U.S.);
* You have resided within a state or district for at least 3 months;
* You must be a person of good moral character (certain crimes such as aggravated felony, drug related, gambling offenses, prostitution, etc. will most likely disqualify an applicant);
* You can read, write, speak and understand basic English;
* You have a basic knowledge of US history and government (see test questions);
* You must show attachment to the principles of the Constitution;
* You may also apply for citizenship if
1. you have been a lawful permanent resident for 3 years if you obtained LPR status based on a marriage to a U.S. citizen, and you have been married to and living with the same citizen for the past three years (Note that the 3-year period starts with the date your green card is approved, even if it is a conditional green card); or,
2. you have served in the U.S. Armed Forces; or,
3. you belong to one of several groups eligible for naturalization (e.g. people who are nationals but not citizens).