S.D. Codified Laws § 47-1A-725
Shares entitled to vote as a separate voting group may take action on a matter at a meeting only if a quorum of those shares exists with respect to that matter. Unless the articles of incorporation or this chapter provide otherwise, a majority of the votes entitled to be cast on the matter by the voting group constitutes a quorum of that voting group for action on that matter. Once a share is represented for any purpose at a meeting, it is deemed present for quorum purposes for the remainder of the meeting and for any adjournment of that meeting unless a new record date is or must be set for that adjourned meeting. If a quorum exists, action on a matter, other than the election of directors, by a voting group is approved if the votes cast within the voting group favoring the action exceed the votes cast opposing the action, unless the articles of incorporation or this chapter require a greater number of affirmative votes. An amendment of articles of incorporation adding, changing, or deleting a quorum or voting requirement for a voting group greater than specified in this section is governed by § 47-1A-727.
SDCL 47-1A-725