During the sixteenth and seventeenth centuries, all european nations had established churches, and religious wars between nations (and sometimes within them) were fierce.
(a) true
(b) false

True.

Explanation:

The given statement is true.

The wars of religion in European were a set of holy wars that began in the centuries 16th, 17th and 18th. The wars that were fought following the Protestant Reformation occurred in the year 1517,  agitated the political and religious harmony in the European Catholic nations. Religion was not the only cause for the religious wars but it also included the territorial ambitions, uprisings, and Great Power struggles.