Final answer:
Sudden infant death syndrome (SIDS) is the leading cause of infant death in the United States.
Correct option is A.
Step-by-step explanation:
The leading cause of infant death in the United States is sudden infant death syndrome (SIDS). SIDS is the unexplained death of a seemingly healthy infant, usually during sleep. It is one of the leading causes of death in the first year of life, with about two thousand infants dying from SIDS in the U.S. each year.