Colleen receives most of her income from wages from her job as a high school teacher. She also receives supplemental income from freelance tutoring part-time during the summer. Because her tutoring income is not subject to withholding, Colleen is concerned that she will have a balance due at the end of the year. Which of the following is an option you can recommend to Colleen to avoid a balance due?

A) Claim an exemption from withholding.

B) Investigate whether she qualifies to classify her tutoring income as a hobby rather than as business income.

C) Send a notarized letter to her employer requesting that they withhold additional amounts from her pay each month.

D) Use the IRS Tax Withholding Estimator to determine her estimated tax obligation and complete a new Form W-4 if necessary.