The parent of a 4 month old infant is concerned because the infant does not yet sit by oneself. What is the nurse's best response?

Most infants sit unsupported at 4 months; this may indicate the infant is slightly delayed.

Most infants do not sit unsupported until 8 months; this infant is normal.

Most infants do not sit unsupported until 12 months; this infant is normal.

Most infants sit unsupported at 6 months; this infant is normal.