Choice "d" is correct. This question combines the rules of estate taxation and gift taxation. Carter's investment in the stock was $50 per share when he died. Upon Carter's death, the stock received a step-up in basis to the fair market value at the date of death (or six months later, if the alternate lower valuation date was elected). Therefore, the stock's basis was $100 per share when it was transferred to Boone. [Note that no capital gain was reportable for the step-up in basis from $50 to $100; however, Carter's estate included the stock at its fair market value of $100/share for estate tax purposes and likely paid a large amount of estate tax on that.] Further, regardless of how long Carter owned the stock (i.e., it could have only been owned for one day), it was automatically deemed long-term property upon Carter's death. So, Boone had 100 shares of stock at a basis of $100/share when Boone received the inheritance. Then, there was a 2-for-1 stock split on April 1 of the following year. This transaction caused Boone to now have double the amount of shares (or, 200 shares) at half the basis per share (or, $50/share). [Note that the total basis remains unchanged (i.e., $100 x 100 shares = $10,000 and $50 x 200 shares = $10,000).] When Boone gifted the stock to Dixon (note: it would not have mattered if Dixon had not been a relative), the donee (Dixon) received the stock at the carryover basis of the donor (Boone). The 100 shares gifted to Dixon were shares from after the stock split; therefore, they have a basis of $50 per share, or a total basis of $5,000 for the 100 shares. [Note that Boone still has 100 shares at a basis of $50 as well.]

Choices "a", "c", and "b" are incorrect, per the above discussion.