Compare the three types of redemptions (i.e., substantially disproportionate, not essentially equivalent to a dividend, and complete termination of shareholder interest) in terms of the following features:

a. Often permissible, even where percentage stock ownership does not decrease by more than 80%.
b. Constructive ownership rules may be waived under certain conditions.
c. Treated as an exchange taxed as a capital gain or loss.
d. Stock not surrendered in exchange for corporate distribution.