A shareholder's adjusted basis in the shareholder's stock in an S corporation is used to make determinations with respect to which of the following?
a. the extent to which a distribution made by the corporation to the shareholder is taxable.
b. the amount of losses that shareholders may deduct in a given year, subject to any other limitations that may apply.
c. the shareholder's realized gain or loss upon the sale or exchange of the stock.
d. all of the above.