Concept:A rigid constitution has a difficult amendment process that often requires direct popular approval.
Explanation:A plebiscite or referendum means the people must vote before the constitution can be changed.
This special procedure makes amendment formal and hard to carry out.
Such a constitution is called a
rigid constitution.
A flexible constitution, on the other hand, can be changed easily by the ordinary legislature.
Written and unwritten constitutions refer to how the rules are codified, not how they are amended.
Therefore, the key feature of requiring a referendum points to a rigid constitution.
Answer:C. rigid