Concept:A rigid constitution is one that can only be changed through a difficult and special procedure.
Explanation:Such a constitution does not allow amendments through ordinary law-making processes.
It usually demands a special majority, a lengthy procedure, or multiple stages of approval.
Because of these strict requirements, changing it becomes complicated.
This does not mean the constitution is easy to review or accessible to everyone.
It also does not make the constitution infallible; rigidity only affects the process of change.
Thus, the key feature of a rigid constitution is that its amendment process is difficult.
Answer:D. complicated for amendment