Option A — One
Infant Mortality Rate (IMR) indicates the number of children that die before the age of one year per 1000 live births in that particular year.
IMR is a standard health indicator used to measure development. The age threshold is 1 year (one year). This is a straightforward factual recall question — just select Option A. Remember: IMR is one of the key health statistics mentioned alongside literacy rate and per capita income when comparing development across states/countries.