According to the PCAOB, which of the following tax services would impair independence? A. Tax consulting B. Providing a tax opinion where the opinion is not considered an aggressive position or listed transaction by the IRS C. Tax returns prepared by BDO Spain for the controller's dependent children living in Spain while attending school abroad D. Tax consulting for the CFO of an IPO candidate completed before the start of the professional engagement period for the audit of the financial statements to be included in the IPO registration