Answer the following Homonyms:

_____________ is the most important city of a country.

In the sentence "___________ is the most important city of a country," the correct homonym to use is "capital." The word "capital" refers to the city that serves as the seat of government and the administrative centre of a country. 

While "capitol" sounds similar, it specifically refers to a building where legislative bodies meet, not a city. The other options, "capetol" and "capitalisation," are either incorrect or unrelated in meaning. Therefore, the correct answer is option c: capital.