The basic importance of any written constitution is to
a) ensure that all people have a right to speak their mind.
b) prevent communist groups from controlling the government.
c) allow political parties to form and run the government.
d) define rights of citizens and the principles and powers of government.

A Constitution is written in order to secure a compromise. The importance of this compromise is that it is defining the rights of citizens and the principles and powers of government (D).

A written Constitution serves to establish and to concretize the powers that are making it. It is written so it can be read by everyone and especially because this turns it into something permanent. It is a way to make a lasting compromise between all that participated in its writing.

the exclusive possession or control of the supply or trade in a commodity or service.