Assuming the gift tax exclusion is $15,000, which of the following gifts will require a taxpayer to file a gift tax return? A. $18,000 paid directly to a bank to pay off a loan on behalf of the taxpayer's friend. B. $20,000 for medical expenses paid directly to a hospital on behalf of the taxpayer's friend. C. $25,000 for campaign expenses paid to a charitable organization. D. $45,000 for tuition paid directly to an accredited university on behalf of the taxpayer's niece