Which of the following BEST describes the refundable portion of Part I tax? O A. The refundable portion of Part I tax is equal to additional refundable tax on investment income (ART) of 10 2/3% of aggregate investment income. OB. The refundable portion of Part I tax is calculated as 30 2/3% of the least of aggregate investment income, taxable income, and Part I federal tax for a corporation OC. The purpose of refunding a portion of Part I tax is to reduce the overall tax rate on investment income earned by a CCPC, which allows a CCPC to temporarily shelter passive income from high individual tax rates. OD. The purpose of refunding a portion of Part I tax is that with the inclusion of additional refundable tax on investment income (ART), tax on investment income earned by a CCPC is too high, creating an imperfection in the system of integration