If you realize that you cannot complete your coursework by the end of the term (semester) in which you are enrolled, you may contact your instructor to make a formal petition for a grade of incomplete, "I." Your instructor is not required to give you a grade of incomplete; he/she will make that decision based on the work you have already submitted, and on your personal circumstance.
"The K-State Incomplete Grade Policy states that the grade of Incomplete (I) is given in regular courses (other than independent studies, research, and problems) upon request of the student for personal emergencies that are verifiable. The faculty member has the responsibility to provide written notification to the student of work required to remove the Incomplete. The student has the responsibility to take the initiative in completing the work, and is expected to make up the Incomplete during the first term (enrolled) at the university after receiving the grade of I. If the student does not make up the Incomplete during the first term enrolled at the university after receiving it, a grade may be given by the faculty member without further consultation with the student.
If after the end of the first term the I remains on the record it will be designated as F for record-keeping purposes and will be computed in the student's GPA, weighted at 0 points per credit. A grade of NR will be treated in a like manner using the designation F" (quote from "grades" in the University catalog).