By his or her first birthday, an infant's weight typically ________.

By the time an infant reaches their first birthday, it is expected that their weight will have tripled from their birth weight. This significant increase in weight is part of the normal growth and development pattern seen in infants, as they rapidly gain weight during the first year of life due to several factors, including nutritional needs and developmental milestones.

Infants are typically expected to gain about an ounce a day during the first few months, leading to this tripling effect by the one-year mark. This growth pattern indicates that the infant is receiving adequate nutrition to support their physical and neurological development, which is crucial in these early stages of life.

The other options do not accurately reflect the typical growth trajectory of infants during this crucial developmental period.