Yes candidates who are unmarried male and their age lie between 16.5 and 19.5 years are eligible to appear in exam. Education qualification includes that candidates have to pass or appear in class 12 (10+2) examination. For more details candidates can check NDA eligibility criteria
Only to be 17 year of age is not going to be sufficient for your NDA . You also have to be at least appearing in intermediate. Not to worry much just study hard by focusing on your English and maths mainly you can surely crack it in Next to next year of 10+2 appearing.
Ok good luck