You must demonstrate knowledge of U.S. history and civics.
During the citizenship interview, the USCIS office will randomly ask you 10 questions about U.S. history and civics (taken from this list of 100 possible questions).
For most people, the questions will be asked verbally and in English (unless you meet the requirements listed above to bypass the English language requirement). You must answer 6 out of the 10 questions correctly to pass.
If you are at least 65 and have been a Legal Permanent Resident for at least 20 years, you can study from a list of just 20 questions. You will be asked 10 out of 20 questions and you must answer 6 correctly to pass.
If you have certain medical conditions that make it impossible for you to learn new information, you may not have to take either exam. A medical doctor or psychiatrist must complete Form N-648: Medical Certification for Disability Exceptions. Examples of medical conditions that can qualify for the N-648 waiver include a traumatic brain injury, stroke, dementia, or PTSD.