There Are Four Methods That Have Been Used in Distributing

There are four methods that have been used in distributing new securities of central governments. Which of the below is NOT one of these?

A) One of these is the regular calendar auction/Dutch-style system.
B) One of these is the ad hoc auction system.
C) One of these is the top system/maximum-price offering system.
D) One of these is the regular calendar auction/minimum-price offering system.