Which group of motions typically requires a two-thirds vote?

In parliamentary procedure, certain motions require a two-thirds vote to protect the rights of the minority while ensuring that a decision can be made efficiently. The correct group of motions that typically requires a two-thirds vote includes motions that may significantly alter the discussion's flow or the assembly's established rules.

The motions listed in the correct choice include the "previous question," which is a motion to end debate and bring the assembly to a vote, and "suspend the rules," which allows the assembly to set aside its established rules temporarily for a specific purpose. Additionally, "limit or extend limits of debate" modifies the rules governing how long members can debate a motion. These actions are significant because they can have a profound impact on the decision-making process; therefore, requiring a higher threshold for approval helps ensure that there's substantial consensus among members before proceeding.

The other groups of motions mentioned in the alternatives either do not uniformly require such a high vote threshold or consist of different types of motions. For instance, point of order and incidental motions do not require a two-thirds vote, while the motions related to amendments and postponement typically require a simple majority. Understanding these nuances helps clarify why certain motions have increased requirements for approval.