The correct answer is D) submit an application to the INS.
You are over the age of 18, have been in the country for six years, and have learned English. Your next step toward becoming a citizen is to "submit an application to the INS."
You also have to show the immigration authorities that you are a person of values and good moral character, demonstrate your attachments to the United States principles established in the Constitution and show a proper understanding of the history and government of the US. Then you prepare and submit form N.-400, which is the application for naturalization.