The state constitution- and the formation of the instruments of government- is based
a) free enterprise
b) direct democracy
c) primary elections
d) republic democracy

D) republic democracy

Explanation:

A democratic republic is a republic that takes certain aspects of democracy to make its own version of a way of government, in this case the citizens vote and elect its representatives, and its formed by different states that come together. A direct democracy, which is the other way of government among the options, is a democracy where eveyrone has a saying in the decisions that are made in the country.

(D) Republic democracy

Explanation:

 The republic democracy is one of the government form in which the state is administered by agents of the resident body.

 Since residents don't administer the state themselves yet through delegates, republics might be recognized from direct majority rule government, however present day agent vote based systems are all things considered republics. A republic word comes from the Latin word "Public matter".

Therefore, Option (D) is correct.