Terrorism is a serious hazard to the country.

Answer: Option C

Hazard : a danger or risk.
Chance : a possibility of something happening.
Peril : serious and immediate danger.
Safety : the condition of being protected from or unlikely to cause danger, risk, or injury.
Problem : a matter or situation regarded as unwelcome or harmful and needing to be dealt with and overcome.

Antonym of Hazard is Safety