The war . . . . . . . . badly damaged the country's infrastructure.

Answer: Option C

First-person, second-person, and plural third-person conjugations that use the pronouns I, you, we, and they require the writer to use 'have'. Singular third-person conjugations use ‘has’. These pronouns include he, she, and it. ‘The war’ is singular third person and therefore ‘has’ will be used.