In IMR, age of infants is considered –: (A) Below 1 month, (B) Below 1 year, (C) Upto 1 year, (D) 28 days
Answer is B. Infants are children less than 1 year of age.

Infant mortality rate
"The ratio of infant death in a year to the total number of live birth in that year. But it is usually expressed as a rate per 1000 live birth".